ARM: imx: m53menlo: Do not fail boot on invalid splash screen

None of these splash screen loading errors are so critical as to
justify complete failure to boot, so just print error message as
needed and return 0, the boot can very likely continue without
the splash.

Fix a couple of missing free(dst) instances as well.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP i.MX U-Boot Team <uboot-imx@nxp.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>