regmap: Fix regmap_bulk_read in BE mode

In big endian mode regmap_bulk_read gives incorrect data
for byte reads.

This is because memcpy of a single byte from an address
after full word read gives different results when
endianness differs. ie. we get little-end in LE and big-end in BE.

Signed-off-by: Arun Chandran <achandran@mvista.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>