msm: ipa: remove ipa rm deprecated mechanism support

RM isn't in use for newer devices.

Acked-by: Tal Gelbard <tgelbard@qti.qualcomm.com>
Change-Id: I8005f02acbd424e0721c2efa49f840f2cf7e8f7b
Signed-off-by: Amir Levy <alevy@codeaurora.org>