MIPS: FW: Fix parsing u-boot environment

When reading u-boot's key=value pairs it should skip the '=' and not
use the next argument.

Signed-off-by: Alban Bedel <albeu@free.fr>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8357/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>