omap3_pandora: Switch to using "load" command to load the autoboot script.

CONFIG_CMD_FS_GENERIC is enabled; use it to load the autoboot script,
rather than first attempting with fatload and falling back to
ext2load.

Signed-off-by: Vagrant Cascadian <vagrant@debian.org>
Acked-by: Grazvydas Ignotas <notasas@gmail.com>