MIPS: microMIPS: Remove unsupported compiler flag.

Remove usage of -mno-jals compiler flag when building a pure
microMIPS kernel. The -mno-jals flag only ever existed within
Mentor toolchains. Dropping this flag allows all FSF toolchains
to work.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Reviewed-by: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6200/