arch: arm: Fix armv7 init code

Fix armv7 init code to add isb macro instead of isb function.
Fix L2 cache invalidate code as per arm manual section B2-17.
Use SCTLR (System Control Register) to enable & disable caches
instead of ACTLR (Auxiliary control Register). Replace hand
coded assembly with armv7 ISA.

Change-Id: I740757a2a812d0f70a4c170af4065b4ff14e88e3
4 files changed