arm: omap4: panda: Add reading of the board revision

Detect if we are running on a panda revision A1-A6,
or an ES panda board. This can be done by reading
the level of GPIOs and checking the processor revisions.
This should result in:
Panda 4430:
     GPIO171, GPIO101, GPIO182: 0 1 1 => A1-A5
     GPIO171, GPIO101, GPIO182: 1 0 1 => A6
Panda ES:
     GPIO2, GPIO3, GPIO171, GPIO48, GPIO182: 0 0 0 1 1 => B1/B2
     GPIO2, GPIO3, GPIO171, GPIO48, GPIO182: 0 0 1 1 1 => B3

Set the board name appropriately for the board revision that
is detected.

Update the findfdt macro to load the a4 device tree binary.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
[trini: %s/CONTROL_PADCONF_CORE/(*ctrl)->control_padconf_core_base/ and
 formatting for that]
Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/include/configs/omap4_common.h b/include/configs/omap4_common.h
index f47d52e..2fa4382 100644
--- a/include/configs/omap4_common.h
+++ b/include/configs/omap4_common.h
@@ -178,6 +178,8 @@
 			"setenv fdtfile omap4-sdp.dtb; fi; " \
 		"if test $board_name = panda; then " \
 			"setenv fdtfile omap4-panda.dtb; fi;" \
+		"if test $board_name = panda-a4; then " \
+			"setenv fdtfile omap4-panda-a4.dtb; fi;" \
 		"if test $board_name = panda-es; then " \
 			"setenv fdtfile omap4-panda-es.dtb; fi;" \
 		"if test $fdtfile = undefined; then " \