powerpc/configs: Drop no longer needed PCI_MSI on powernv

In commit a311e738 ("powerpc/powernv: Make PCI non-optional") we
made PCI (and therefore PCI_MSI) non-optional on powernv, so it
doesn't need to be in the defconfig anymore.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/configs/powernv_defconfig

@@ -60,7 +60,6 @@ CONFIG_PPC_64K_PAGES=y
 CONFIG_PPC_SUBPAGE_PROT=y
 CONFIG_SCHED_SMT=y
 CONFIG_PM=y
-CONFIG_PCI_MSI=y
 CONFIG_HOTPLUG_PCI=y
 CONFIG_NET=y
 CONFIG_PACKET=y