Revert "mhi: core: Handle RSC minimum credit requirement"

This reverts commit 64cf7e44.
Change is causing data stall because number of buffers queued
after receiving OOB event is less than 8 and door bell is not rung
until 8 buffers are queued.

Change-Id: I09b23690cfd080955ceb864f28e9d19c22d0bc6b
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>