mhi: core: Increase RSC credit to 10

Change RSC credit limit from 8 to 10 to ensure
that there are sufficient credits even if IPA
processes TRBs while host is about ring the DB.

Change-Id: I2e4593ff0ceccb3491bead326bab0d7d5b4a3e03
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>