MIPS: Kconfig: Fix indentation and add endif comment

The convention for indentation seems to be a single tab. Help text is
further indented by an additional two whitespaces. Fix the lines that
violate these rules.

While add it, add a missing trailing endif comment.

Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>