baytrail: Add functions to peek at GPIO input values

- Add functions to peek at GPIO input pad values (need to be used from
  romstage for board ram_id GPIOs)
- Modify UART GPIOs to use existing fn-assignment function

TEST=Manual. Add debug print and verify that GPIO functions return input
values. Also, verify UART still functions in romstage.
BUG=chrome-os-partner:22865

Change-Id: Ib2e57631c127a592cfa20ab6e2184822424e9d77
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/172189
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/4870
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

src/soc/intel/baytrail/gpio.c

@@ -44,7 +44,7 @@ static const u8 gpssus_gpio_to_pad[GPSSUS_COUNT] =
         { 29, 33, 30, 31, 32, 34, 36, 35, 38, 37,
           18,  7, 11, 20, 17,  1,  8, 10, 19, 12,
            0,  2, 23, 39, 28, 27, 22, 21, 24, 25,
-          26, 51, 56, 54, 49, 55, 48, 47, 50, 58,
+          26, 51, 56, 54, 49, 55, 48, 57, 50, 58,
           52, 53, 59, 40 };
 
 /* GPIO bank descriptions */