ARM: 7271/1: Fix typo in conversion of ARCH_NR_GPIOS to Kconfig

Commit 44986ab0 "ARM: 7240/1: Make ARCH_NR_GPIO a Kconfig variable"
spelled ARCH_NR_GPIOS as ARCH_NR_GPIO, hence making the change
ineffective. This change fixes that.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>