x86/apic/msi: Enable MSI_FLAG_PCI_MSIX_ALLOC_DYN

x86 MSI irqdomains can handle MSI-X allocation post MSI-X enable just out
of the box - on the vector domain and on the remapping domains,

Add the feature flag to the supported feature list
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221124232326.787373104@linutronix.de

arch/x86/include/asm/msi.h

@@ -63,7 +63,7 @@ struct msi_msg;
 u32 x86_msi_msg_get_destid(struct msi_msg *msg, bool extid);
 
 #define X86_VECTOR_MSI_FLAGS_SUPPORTED					\
-	(MSI_GENERIC_FLAGS_MASK | MSI_FLAG_PCI_MSIX)
+	(MSI_GENERIC_FLAGS_MASK | MSI_FLAG_PCI_MSIX | MSI_FLAG_PCI_MSIX_ALLOC_DYN)
 
 #define X86_VECTOR_MSI_FLAGS_REQUIRED					\
 	(MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS)