Several (15) drivers in media/usb/gspca use IF_ENABLED(CONFIG_INPUT)
to decide if they should call input* interfaces, but those drivers
do not build successfully when CONFIG_INPUT=m and the gspca drivers
are builtin (=y).  Making USB_GSPCA depend on INPUT || INPUT=n
fixes the build dependencies and allows all of them to build
cleanly.

Fixes these build errors (selections, not all are listed):

drivers/built-in.o: In function `gspca_disconnect':
(.text+0x32ed0f): undefined reference to `input_unregister_device'
drivers/built-in.o: In function `sd_isoc_irq':
konica.c:(.text+0x333098): undefined reference to `input_event'
konica.c:(.text+0x3330ab): undefined reference to `input_event'
drivers/built-in.o: In function `sd_stopN':
konica.c:(.text+0x3338d3): undefined reference to `input_event'
konica.c:(.text+0x3338e5): undefined reference to `input_event'
drivers/built-in.o: In function `ov51x_handle_button':
ov519.c:(.text+0x335ddb): undefined reference to `input_event'
drivers/built-in.o:ov519.c:(.text+0x335ded): more undefined references to `input_event' follow
pac7302.c:(.text+0x336ea1): undefined reference to `input_event'
pac7302.c:(.text+0x336eb3): undefined reference to `input_event'
drivers/built-in.o: In function `sd_pkt_scan':
spca561.c:(.text+0x338fd8): undefined reference to `input_event'
drivers/built-in.o:spca561.c:(.text+0x338feb): more undefined references to `input_event' follow
t613.c:(.text+0x33a6fd): undefined reference to `input_event'
drivers/built-in.o:t613.c:(.text+0x33a70f): more undefined references to `input_event' follow
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc:	Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>