msm_serial_hs: Fix return value handling from platform_get_irq_by_name

platform_get_irq_by_name function returns -ENXIO upon failure.
The return code should be checked for this error code to detect
failures.

CRs-Fixed: 566710
Change-Id: I95b601edf457a19ad8f617700697fae9b5db0f1f
Signed-off-by: Naveen Kaje <nkaje@codeaurora.org>