misc: Kconfig: add a new dependency for HISI_HIKEY_USB

misc: Kconfig: add a new dependency for HISI_HIKEY_USB

As warned by Randy:

	on x86_64:
	CONFIG_USB_ROLE_SWITCH=m
	and HISI_HIKEY_USB=y.

	ld: drivers/misc/hisi_hikey_usb.o: in function `hisi_hikey_usb_remove':
	hisi_hikey_usb.c:(.text+0x61): undefined reference to `usb_role_switch_unregister'
	ld: hisi_hikey_usb.c:(.text+0xa4): undefined reference to `usb_role_switch_put'
	ld: drivers/misc/hisi_hikey_usb.o: in function `hub_usb_role_switch_set':
	hisi_hikey_usb.c:(.text+0xd3): undefined reference to `usb_role_switch_get_drvdata'
	ld: drivers/misc/hisi_hikey_usb.o: in function `relay_set_role_switch':
	hisi_hikey_usb.c:(.text+0x54d): undefined reference to `usb_role_switch_set_role'
	ld: drivers/misc/hisi_hikey_usb.o: in function `hisi_hikey_usb_probe':
	hisi_hikey_usb.c:(.text+0x8a5): undefined reference to `usb_role_switch_get'
	ld: hisi_hikey_usb.c:(.text+0xa08): undefined reference to `usb_role_switch_register'
	ld: hisi_hikey_usb.c:(.text+0xa6e): undefined reference to `usb_role_switch_put'

Make it dependent on CONFIG_USB_ROLE_SWITCH.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/0e49432d0db9ee8429a9923a1d995935b6b83552.1602047370.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>