AArch32: Fix SCTLR context initialization ...

This patch fixes a bug in context management library when writing
SCTLR register during context initialization. The write happened
prior to initialization of the register context pointer. This
resulted in the compiler optimizing the write sequence from the
final binary and hence SCTLR remains uninitialized when
entering normal world. The bug is fixed by doing the
initialization of the register context pointer earlier in the
sequence.

Change-Id: Ic7465593a74534046b79f40446ffa1165c52ed76

AArch32: Add support in TF libraries ...

This patch adds AArch32 support to cpu ops, context management,
per-cpu data and spinlock libraries. The `entrypoint_info`
structure is modified to add support for AArch32 register
arguments. The CPU operations for AEM generic cpu in AArch32
mode is also added.

Change-Id: I1e52e79f498661d8f31f1e7b3a29e222bc7a4483