platform: msm: msm_bus: Fix bus rule update API definition

msm_bus_rules.h had a typo in the definition of the
msm_bus_rule_update API. This is a fix for that typo.

Change-Id: If1afe114f8c57020855b85dd17d8f54eea315a1a
Acked-by: AJ Lindell <alindell@qti.qualcomm.com>
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>