icnss2: Avoid assert on QMI send failure

There is possibility that ICNSS asserts on QMI send failure
even after receiving FW down indication. To avoid such scenario
check for FW down before ASSERT.

Change-Id: I68981879601e6fba459e9b48405eed370e00e6c6
Signed-off-by: Naman Padhiar <npadhiar@codeaurora.org>