msm: mhi_dev: Do not error out if unable to send MSI

Do not return error if MSI is not yet enabled by the host
in device reboot scenario. Host will check the mhi status
and issue a reset if syserr state is set.

Change-Id: Ie2204d8b750f2939ac7dd6571cbe31ef211e2053
Signed-off-by: Siva Kumar Akkireddi <sivaa@codeaurora.org>