rpmsg: qcom_smd: Fix uninitialized return variable in __qcom_smd_send()

rpmsg: qcom_smd: Fix uninitialized return variable in __qcom_smd_send()

The "ret" variable isn't initialized if we don't enter the loop.  For
example,  if "channel->state" is not SMD_CHANNEL_OPENED.

Fixes: 33e3820dda88 ("rpmsg: smd: Use spinlock in tx path")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/aAkhvV0nSbrsef1P@stanley.mountain
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>