msm: Kconfig: Enable ARCH_WANT_KMAP_ATOMIC_FLUSH for msmferrum

Targets with content protection (potentially) backed by
highmem need to ensure that all potential mappings are
removed. Enable ARCH_WANT_KMAP_ATOMIC_FLUSH to ensure
that old kmap_atomic mappings get flushed.

Change-Id: I44d9057599584ca531a89c856fd7c4788eb45de5
Signed-off-by: Kishan Kumar <kishank@codeaurora.org>