arm64: Kconfig: select HISILICON_IRQ_MBIGEN only if PCI is selected

Even when PCI is disabled, ARCH_HISI selects HISILICON_IRQ_MBIGEN
triggerring the following config warning:

warning: (ARM64 && HISILICON_IRQ_MBIGEN) selects ARM_GIC_V3_ITS which
	has unmet direct dependencies (PCI && PCI_MSI)

This patch makes selection of HISILICON_IRQ_MBIGEN conditional on PCI.

Cc: Ma Jun <majun258@huawei.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>