msm: add gpio driver for single-core SoCs.

Install a gpiolib driver supporting the on-chip gpios for
single-core MSMs in the 7x00 family, including 7x00A, 7x25, 7x27,
7x30, 8x50, and 8x50a.

As part of the ongoing effort to converge on a common code base,
this driver is based on the Google-Android msmgpio driver, whose
authors include Brian Swetland and Arve Hjønnevåg.

Cc: Arve Hjønnevåg <arve@android.com>
Cc: H Hartley Sweeten <hartleys@visionengravers.com>
Cc: Ryan Mallon <ryan@bluewatersys.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Gregory Bean <gbean@codeaurora.org>
Signed-off-by: Daniel Walker <dwalker@codeaurora.org>