Documentation: PCI: Fix typos in msi-howto.rst

Fix subject-verb agreement for "has a requirements" as well as
"neither...or" conjunction mistake. And convert "Message Signalled
Interrupts" to "Message Signaled Interrupts" to match the PCIe spec.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://patch.msgid.link/1766713528-173281-1-git-send-email-shawn.lin@rock-chips.com

Author: shawn1221

Documentation/PCI/msi-howto.rst

@@ -98,7 +98,7 @@ function::
 
 which allocates up to max_vecs interrupt vectors for a PCI device.  It
 returns the number of vectors allocated or a negative error.  If the device
-has a requirements for a minimum number of vectors the driver can pass a
+has a requirement for a minimum number of vectors the driver can pass a
 min_vecs argument set to this limit, and the PCI core will return -ENOSPC
 if it can't meet the minimum number of vectors.
 
@@ -127,7 +127,7 @@ not be able to allocate as many vectors for MSI as it could for MSI-X.  On
 some platforms, MSI interrupts must all be targeted at the same set of CPUs
 whereas MSI-X interrupts can all be targeted at different CPUs.
 
-If a device supports neither MSI-X or MSI it will fall back to a single
+If a device supports neither MSI-X nor MSI it will fall back to a single
 legacy IRQ vector.
 
 The typical usage of MSI or MSI-X interrupts is to allocate as many vectors
@@ -203,7 +203,7 @@ How to tell whether MSI/MSI-X is enabled on a device
 ----------------------------------------------------
 
 Using 'lspci -v' (as root) may show some devices with "MSI", "Message
-Signalled Interrupts" or "MSI-X" capabilities.  Each of these capabilities
+Signaled Interrupts" or "MSI-X" capabilities.  Each of these capabilities
 has an 'Enable' flag which is followed with either "+" (enabled)
 or "-" (disabled).