msm: idle-v7: Fix for THUMB2 builds

Assembly functions need ENDPROC so that the assembler can
determine that the functions are thumb vs. arm. Otherwise a blx
will be generated causing us to switch into arm mode when we
still want to execute thumb code. Also, you can't use sp in the
register list of ldm/stm instructions, so remove it in thumb
builds and do the load/store separately.

Change-Id: I864d2ff2805a49d8fd96a2e90ca16a5511da6577
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>