Davinci: gpio - register layout invariant inlines

This patch renders the inlined gpio accessors in gpio.h independent of the
underlying controller's register layout.  This is done by including three new
fields in davinci_gpio_controller to hold the addresses of the set, clear, and
in data registers.

Other changes:

1. davinci_gpio_regs structure definition moved to gpio.c.  This structure is
no longer common across all davinci socs (davinci_gpio_controller is).

2. controller base address calculation code (gpio2controller()) moved to
gpio.c as this was no longer necessary for the inline implementation.

3. modified inline range checks to use davinci_soc_info.gpio_num instead of
DAVINCI_N_GPIO.

Signed-off-by: Cyril Chemparathy <cyril@ti.com>
Tested-by: Sandeep Paulraj <s-paulraj@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>