icnss: Do not assert if reboot requested during PDR

When icnss driver sees a PD down, and if the recovery is already in
progress, it forces an assert in debug builds. That is to detect any
Modem failures during PDR or to catch any instance of recursive PDRs.
When system goes thru a reboot or shutdown, and if the recovery is in
progress then avoid calling this assert.

CRs-Fixed: 2135071
Change-Id: I28f5c79a4cd8b83f60a62111535b11c2fba6000b
Signed-off-by: Sameer Thalappil <sameert@codeaurora.org>