Revert "elf-loader: warn about invalid endianness"

This reverts c8e1158c "elf-loader: warn about invalid endianness"
as it produces a useless message every time an LE kernel image is
passed via -kernel on a ppc64-pseries machine. The pseries machine
already checks for ELF_LOAD_WRONG_ENDIAN and tries with big_endian=0.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Yongbok Kim <yongbok.kim@imgtec.com>