defconfig: sun50iw1: Add improved boot procedure

This implements booting procedure similar to mainline u-boot that
supports using separate /boot partition of any FS type as well as single
partition images
Also boot environment file (uEnv.txt) will be loaded only if the file
exists, so no error messages will be printed if the file doesn't exist

include/configs/sun50iw1p1.h

@@ -352,7 +352,9 @@
 	"initrd_filename=initrd.img\0" \
 	"bootenv_filename=uEnv.txt\0" \
 	"load_bootenv=" \
-		"fatload mmc ${boot_part} ${load_addr} ${bootenv_filename}\0" \
+		"if test -e mmc ${boot_part} ${bootenv_filename}; then " \
+			"load mmc ${boot_part} ${load_addr} ${bootenv_filename}; " \
+		"fi\0" \
 	"import_bootenv=" \
 		"env import -t ${load_addr} ${filesize}\0" \
 	"load_dtb=" \
@@ -368,7 +370,13 @@
 		"fatload mmc ${boot_part} ${initrd_addr} ${initrd_filename}; "\
 		"setenv initrd_size ${filesize}\0" \
 	"load_bootscript=" \
-		"fatload mmc ${boot_part} ${load_addr} ${script}\0" \
+		"for prefix in / /boot/; do " \
+			"if test -e mmc ${boot_part} ${prefix}${script}; then " \
+				"load mmc ${boot_part} ${load_addr} ${prefix}${script}; " \
+				"echo Booting with script ...; " \
+				"run scriptboot; "\
+			"fi; "\
+		"done\0" \
 	"scriptboot=source ${load_addr}\0" \
 	"set_cmdline=" \
 		"setenv bootargs console=${console} ${optargs} " \
@@ -380,13 +388,9 @@
 			"echo Loading boot environment ...; " \
 			"run import_bootenv; " \
 		"fi; " \
-		"if run load_bootscript; then " \
-			"echo Booting with script ...; " \
-			"run scriptboot; " \
-		"else " \
-			"echo Booting with defaults ...; " \
-			"run mmcboot; " \
-		"fi\0"
+		"run load_bootscript; " \
+		"echo Booting with defaults ...; " \
+		"run mmcboot; \0"
 
 #define CONFIG_BOOTDELAY	3
 #define CONFIG_BOOTCOMMAND	"run mmcbootcmd"