MIPS: PowerTV: Fix defconfigs for coverage builds
MIPS: PowerTV: Fix defconfigs for coverage builds

The toolchain prefix is most likely be site specific and is not
guaranteed to always be "mips-linux-gnu-", so simply don't specify one.
A quick "git grep" shows this to be consistent amongst other cross
compiled targets.

Signed-off-by: Ralf Baechle <92f48d309cda194c8eda36aa8f9ae28c488fa208@linux-mips.org>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs