DRA7xx has 8 GPIO banks so that there are 32x8 = 256 GPIOs.
In order for the gpiolib to detect and initialize these
and other TWL GPIOs, ARCH_NR_GPIO is set to 512 using the
kconfig default for DRA7.
Signed-off-by: R Sricharan <r.sricharan@ti.com> Signed-off-by: Rajendra Nayak <rnayak@ti.com>