ion: Relax CONFIG_ION_MSM_HEAPS dependencies

Some of the dependencies specified by CONFIG_ION_MSM_HEAPS
aren't actually required for enabling a minimalistic subset
of the MSM ION heaps, so relax these dependencies.

Change-Id: Icc1383ef571dd3e50a536b7cfe2f8c73ffb4279f
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>