board: freescale: p1_p2_rdb_pc: Fix parsing inverted bits from boot input data

On some boards upper 4 bits of i2c boot input data (register 0) are
inverted. Information which bits are inverted is stored in register 2.

So invert read input data back according to register 2 prior processing
them. This fixes printing "rom_loc: value" line during booting.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Peng Fan <peng.fan@nxp.com>