ARM: shmobile: Introduce r8a7790_read_mode_pins()

Break out the r8a7790 boot mode code into a separate
function so it can be shared by multiple users.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

diff --cc arch/arm/mach-shmobile/clock-r8a7790.c
Simple merge

diff --cc arch/arm/mach-shmobile/include/mach/r8a7790.h
Simple merge

diff --cc arch/arm/mach-shmobile/setup-r8a7790.c
Simple merge