msm_serial_hs: Handling spinlocks during error case

In the API where UART driver notifies the top layer
about the errors received with the data, spinlock
is not released and returning from the API.
This patch fixes the issue.

Change-Id: I12b959fed26be5063f8e59cb042c286f73968bd2
Signed-off-by: Dilip Kota <c_dkota@codeaurora.org>