bcma: BCMA_DRIVER_GPIO should depend on GPIOLIB instead of selecting it

bcma: BCMA_DRIVER_GPIO should depend on GPIOLIB instead of selecting it

Commit cf0936b06d8e98a157630e99f647e2ff6d29d7ad ("bcma: add GPIO driver")
added BCMA_DRIVER_GPIO, which unconditionally selects GPIOLIB, causing
a Kconfig warning:

warning: (ARCH_REQUIRE_GPIOLIB && SSB_DRIVER_GPIO && BCMA_DRIVER_GPIO && MFD_TC6393XB && FB_VIA) selects GPIOLIB which has unmet direct dependencies (ARCH_WANT_OPTIONAL_GPIOLIB || ARCH_REQUIRE_GPIOLIB)

and build failure for m68k/allmodconfig:

In file included from include/linux/bcma/bcma.h:8,
                 from drivers/bcma/bcma_private.h:9,
                 from drivers/bcma/main.c:9:
include/linux/bcma/bcma_driver_chipcommon.h:582: error: field ‘gpio’ has incomplete type
In file included from include/linux/bcma/bcma.h:12,
                 from drivers/bcma/bcma_private.h:9,
                 from drivers/bcma/main.c:9:
include/linux/ssb/ssb.h:440: error: field ‘gpio’ has incomplete type
make[4]: *** [drivers/bcma/main.o] Error 1
make[3]: *** [drivers/bcma/] Error 2

Turn the select into a dependency to fix this.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>