powerpc: Use scripts/mkuboot.sh instead of 'mkimage'
powerpc: Use scripts/mkuboot.sh instead of 'mkimage'

mkuboot.sh provides a basic wrapper for the 'mkimage' utility.  Using
mkuboot.sh provides clearer error reporting and allows a toolchain to
use its own 'mkimage' executable specified by ${CROSS_COMPILE}mkimage.
Additionally, this brings PowerPC in line with other architectures
which already call mkimage via mkuboot.sh.

Signed-off-by: Peter Tyser <9bf1de3f247c5d3b495d8f9e25a7c0f96dce3ad4@xes-inc.com>
Signed-off-by: Grant Likely <9069e6f5a2b566e2674a0ba1e2bf39c12c195fad@secretlab.ca>

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