uboot: import first variable from auxiliary environment

The U-Boot env file is generated by
mkenvimage, which prefixes the variable data with a 4-byte CRC32 by default.
ixpreboot.sh previously imported it with `env import -b` as per uboot docs(-b assume binary format (’0’ separated, “00” terminated).),
which treats the buffer as raw binary and does not strip the CRC.
As a result the first variable's name is parsed a part of CRC.
Later variables import correctly because by then the parser is past the CRC.
Switching to `env import -c` as per uboot docs (-c assume checksum protected environment format.)
makes U-Boot validate and strip the CRC before parsing, so the first variable imports under its real name.

Tested on:
- QEMU

Signed-off-by: Ejub Sabic <ejub1946@outlook.com>

board/aarch64/marvell-espressobin/README.md

@@ -154,7 +154,7 @@ setenv bootcmd_net \
 setenv bootcmd \
   'setenv bootpart 2; setenv bootslot primary; setenv auxpart 1; \
    if ext4load mmc 0:$auxpart $loadaddr /uboot.env; then \
-     env import -b $loadaddr $filesize BOOT_ORDER; \
+     env import -c $loadaddr $filesize BOOT_ORDER; \
    fi; \
    if test "$BOOT_ORDER" = "secondary primary" || \
       test "$BOOT_ORDER" = "secondary primary net"; then \

board/common/uboot/scripts/ixpreboot.sh

@@ -33,7 +33,7 @@ for tgt in "${boot_targets}"; do
 	setexpr ixmenu_n ${ixmenu_n} + 1
 
 	if load ${devtype} ${devnum}:${auxpart} ${loadaddr} /uboot.env; then
-	    env import -b ${loadaddr} ${filesize} BOOT_ORDER DEBUG ethact BOARD_VARIANT
+	    env import -c ${loadaddr} ${filesize} BOOT_ORDER DEBUG ethact BOARD_VARIANT
 	    run ixvariant
 	fi