msm_serial_hs: Improve error handing for SPS API usage

SPS APIs sps_connect() and sps_disconnect() are used multiple time in UART
during transmit and receive path. This change adds error check conditions
in UART with usage of sps_connect() and sps_disconnect() API.

Also add fix for the error message seen during uart clock off request.
During uart clock off request, by the UART client driver, sps_disconnect
API is called two times consecutively, first in msm_hs_check_clock_off()
and then followed by msm_hs_stop_rx_locked() by queing the work
disconnect_rx_endpoint. Due to two consecutive sps_disconnect API call,
below error message is seen :
   sps:BAM device of this pipe is NULL

Hence fixing the same error message by removing sps_disconnect() from the
msm_hs_check_clock_off() as calling sps_disconnect() API single time from
msm_hs_stop_rx_locked() is good enough to achieve uart clock off request
functionality.

CRs-Fixed: 474138
Change-Id: I3bcabe2cb6d6efde087a16de30e5400cda4ad74d
Signed-off-by: Saket Saurabh <ssaurabh@codeaurora.org>