am335x_evm: Bring in 'boot_fdt' logic from i.MX

Bring in the 'boot_fdt' environment variable that i.MX boards use to try
and load a device tree when booting.

Signed-off-by: Tom Rini <trini@ti.com>

include/configs/am335x_evm.h

@@ -85,6 +85,7 @@
 	"loadaddr=0x80200000\0" \
 	"fdtaddr=0x80F80000\0" \
 	"fdt_high=0xffffffff\0" \
+	"boot_fdt=try\0" \
 	"rdaddr=0x81000000\0" \
 	"bootdir=/boot\0" \
 	"bootfile=uImage\0" \
@@ -132,6 +133,20 @@
 	"loadramdisk=load mmc ${mmcdev} ${rdaddr} ramdisk.gz\0" \
 	"loaduimage=load mmc ${bootpart} ${loadaddr} ${bootdir}/${bootfile}\0" \
 	"loadfdt=load mmc ${bootpart} ${fdtaddr} ${bootdir}/${fdtfile}\0" \
+	"mmcloados=run mmcargs; " \
+		"if test ${boot_fdt} = yes || test ${boot_fdt} = try; then " \
+			"if run loadfdt; then " \
+				"bootm ${loadaddr} - ${fdtaddr}; " \
+			"else " \
+				"if test ${boot_fdt} = try; then " \
+					"bootm; " \
+				"else " \
+					"echo WARN: Cannot load the DT; " \
+				"fi; " \
+			"fi; " \
+		"else " \
+			"bootm; " \
+		"fi;\0" \
 	"mmcboot=mmc dev ${mmcdev}; " \
 		"if mmc rescan; then " \
 			"echo SD/MMC found on device ${mmcdev};" \
@@ -143,11 +158,7 @@
 				"echo Running uenvcmd ...;" \
 				"run uenvcmd;" \
 			"fi;" \
-			"if run loaduimage; then " \
-				"run loadfdt;" \
-				"run mmcargs; " \
-				"bootm ${loadaddr} - ${fdtaddr};" \
-			"fi;" \
+			"run mmcloados;" \
 		"fi;\0" \
 	"spiboot=echo Booting from spi ...; " \
 		"run spiargs; " \