powerpc/85xx: Read board switch settings on p1_p2_rdb

powerpc/85xx: Read board switch settings on p1_p2_rdb

PCA9557 is parallel I/O expansion device on I2C bus which stores various
board switch settings like NOR Flash-Bank selection, SD Data width.

On board:
switch SW5[6] is to select width for eSDHC
        ON  - 4-bit [Enable eSPI]
        OFF - 8-bit [Disable eSPI]

switch SW4[8] is to select NOR Flash Bank for Booting
        OFF - Primary Bank
        ON  - Secondary Bank

Read board switch settings on p1_p2_rdb and configure corresponding
eSDHC width.

Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com>
Signed-off-by: Dipen Dudhat <dipen.dudhat@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>