bus: mhi: Remove break statement from mhi_process_cmd_completion

mhi_process_cmd_completion API is using if/else statement. This API
on a newer kernel branch is using switch case statement. Due to
automatic propagation break statement got copied. Remove break
statement and use goto.

Change-Id: I1fad42ef95d4e63829d819327c38b3c80f852872
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>