cpu/arm/k60: Remove old assembler startup line.

Was used to build the startup code in assembler, replaced by C recently.
Signed-off-by: Joakim Gebart <joakim.gebart@eistec.se>
cpu/arm/k60: Generate dependency information during build.

This will make incremental builds alot more reliable.

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