rust: pci: fix build failure when CONFIG_PCI_MSI is disabled

When CONFIG_PCI_MSI is disabled pci_alloc_irq_vectors() and
pci_free_irq_vectors() are defined as inline functions and hence require
a Rust helper.

	error[E0425]: cannot find function `pci_alloc_irq_vectors` in crate `bindings`
	    --> rust/kernel/pci/irq.rs:144:23
	     |
	 144 | ...s::pci_alloc_irq_vectors(dev.as_raw(), min_vecs, max_vecs, irq_types.as_raw())
	     |       ^^^^^^^^^^^^^^^^^^^^^ help: a function with a similar name exists: `pci_irq_vector`
	     |
	    ::: .../rust/bindings/bindings_helpers_generated.rs:1197:5
	     |
	1197 |     pub fn pci_irq_vector(pdev: *mut pci_dev, nvec: ffi::c_uint) -> ffi::c_int;
	     |     --------------------------------------------------------------------------- similarly named function `pci_irq_vector` defined here

	error[E0425]: cannot find function `pci_free_irq_vectors` in crate `bindings`
	    --> rust/kernel/pci/irq.rs:170:28
	     |
	 170 |         unsafe { bindings::pci_free_irq_vectors(self.dev.as_raw()) };
	     |                            ^^^^^^^^^^^^^^^^^^^^ help: a function with a similar name exists: `pci_irq_vector`
	     |
	    ::: .../rust/bindings/bindings_helpers_generated.rs:1197:5
	     |
	1197 |     pub fn pci_irq_vector(pdev: *mut pci_dev, nvec: ffi::c_uint) -> ffi::c_int;
	     |     --------------------------------------------------------------------------- similarly named function `pci_irq_vector` defined here

	error: aborting due to 2 previous errors

Fix this by adding the corresponding helpers.

Fixes: 340ccc9 ("rust: pci: Allocate and manage PCI interrupt vectors")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512012238.YgVvRRUx-lkp@intel.com/
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Link: https://patch.msgid.link/20251202210501.40998-1-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Danilo Krummrich

rust/helpers/pci.c

@@ -23,9 +23,21 @@ bool rust_helper_dev_is_pci(const struct device *dev)
 }
 
 #ifndef CONFIG_PCI_MSI
+int rust_helper_pci_alloc_irq_vectors(struct pci_dev *dev,
+				      unsigned int min_vecs,
+				      unsigned int max_vecs,
+				      unsigned int flags)
+{
+	return pci_alloc_irq_vectors(dev, min_vecs, max_vecs, flags);
+}
+
+void rust_helper_pci_free_irq_vectors(struct pci_dev *dev)
+{
+	pci_free_irq_vectors(dev);
+}
+
 int rust_helper_pci_irq_vector(struct pci_dev *pdev, unsigned int nvec)
 {
 	return pci_irq_vector(pdev, nvec);
 }
-
 #endif