ARM: imx_v6_v7_defconfig: enable PCI_MSI

This has been stable on i.MX6 for a good while now and there is no
reason to keep it disabled, as it allows to allocate non-shared
IRQs if several PCIe devices are connected to a single host.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -44,6 +44,7 @@ CONFIG_SOC_IMX6UL=y
 CONFIG_SOC_IMX7D=y
 CONFIG_SOC_VF610=y
 CONFIG_PCI=y
+CONFIG_PCI_MSI=y
 CONFIG_PCI_IMX6=y
 CONFIG_SMP=y
 CONFIG_PREEMPT_VOLUNTARY=y