bcm53xx: drop unused (and broken) GPIOLIB patch

First of all this patch was broken since adding 3.18 for bcm53xx. It was
modifying ARCH_BRCMSTB instead of ARCH_BCM_5301X.
Secondly we don't need it as ARCH_MULTIPLATFORM selects
ARCH_WANT_OPTIONAL_GPIOLIB for us.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

SVN-Revision: 44383