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

arch/mips/Kconfig

@@ -3255,7 +3255,7 @@ menu "CPU Power Management"
 
 if CPU_SUPPORTS_CPUFREQ && MIPS_EXTERNAL_TIMER
 source "drivers/cpufreq/Kconfig"
-endif
+endif # CPU_SUPPORTS_CPUFREQ && MIPS_EXTERNAL_TIMER
 
 source "drivers/cpuidle/Kconfig"