cpu/arm/k60: Makefile refactoring.

CPU makefile refactoring
  - Adds support for quiet builds (default on)
  - Integrate 'bytes' Makefile rule into linking target.
  - Replace perl dependency by awk for size computation.

Get back verbose builds by building with 'make V=1'

Signed-off-by: Joakim Gebart <joakim.gebart@eistec.se>