msm: krait-l2-accessors: Remove set_get_l2_indirect_reg() API

There are no remaining users of this API, which writes to an indirect
register and reads back the new value. To simplify the future addition
of RTB logging for L2 indirect CP15 accesses, remove the unused API.

set_l2_indirect_reg() and get_l2_indirect_reg() can be individually
called to accomplish the same purpose that set_get_l2_indirect_reg()
served, with a negligible performance difference for common usecases.

Change-Id: If372370eabda7cf5d9eee488222a17e139609a36
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>