PCI: rcar-host: Add OF Kconfig dependency to avoid objtool no-cfi warning

After commit 894af4a ("objtool: Validate kCFI calls"), compile
testing pcie-rcar-host.c with CONFIG_FINEIBT=y and CONFIG_OF=n results
in a no-cfi objtool warning in rcar_pcie_probe():

  $ cat allno.config
  CONFIG_CFI=y
  CONFIG_COMPILE_TEST=y
  CONFIG_CPU_MITIGATIONS=y
  CONFIG_GENERIC_PHY=y
  CONFIG_MITIGATION_RETPOLINE=y
  CONFIG_MODULES=y
  CONFIG_PCI=y
  CONFIG_PCI_MSI=y
  CONFIG_PCIE_RCAR_HOST=y
  CONFIG_X86_KERNEL_IBT=y

  $ make -skj"$(nproc)" ARCH=x86_64 KCONFIG_ALLCONFIG=1 LLVM=1 clean allnoconfig vmlinux
  vmlinux.o: warning: objtool: rcar_pcie_probe+0x191: no-cfi indirect call!

When CONFIG_OF is unset, of_device_get_match_data() returns NULL, so
LLVM knows this indirect call has no valid destination and drops the
kCFI setup before the call, triggering the objtool check that makes sure
all indirect calls have kCFI setup.

This driver depends on OF for probing with non-NULL data for every match
so this call will never be NULL in practice. Add a hard Kconfig
dependency on OF to avoid the warning.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202510092124.O2IX0Jek-lkp@intel.com/
Closes: ClangBuiltLinux#2134
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20251014-rcar_pcie_probe-avoid-nocfi-objtool-warning-v2-1-6e0204b002c6@kernel.org

Author: nathanchance

drivers/pci/controller/Kconfig

@@ -243,6 +243,7 @@ config PCI_TEGRA
 config PCIE_RCAR_HOST
 	bool "Renesas R-Car PCIe controller (host mode)"
 	depends on ARCH_RENESAS || COMPILE_TEST
+	depends on OF
 	depends on PCI_MSI
 	select IRQ_MSI_LIB
 	help