am335x_evm: Add support for eMMC environment

Some boards, such as the BeagleBone Black, have an eMMC chip intstead
of NAND. We can use the eMMC boot partition to store the environment,
since it isn't used for anything else. This allows us to have a
configurable environment on those boards.

Signed-off-by: Justin Waters <justin.waters@timesys.com>

include/configs/am335x_evm.h

@@ -502,7 +502,12 @@
 					"512k(u-boot),128k(u-boot-env1)," \
 					"128k(u-boot-env2),3464k(kernel)," \
 					"-(rootfs)"
-#endif /* SPI support */
+#elif defined(CONFIG_EMMC_BOOT)
+#undef CONFIG_ENV_IS_NOWHERE
+#define CONFIG_ENV_IS_IN_MMC
+#define CONFIG_SYS_MMC_ENV_DEV		1
+#define CONFIG_SYS_MMC_ENV_PART		2
+#endif
 
 /* Unsupported features */
 #undef CONFIG_USE_IRQ