msm_serial_hs: Fix the wrong register offset Macro usage

In the msm_hs_tx_empty() API, accessing wrong register offset
macro UARTDM_SR_ADDR.This leading to the unexpected issues
The right register offset macro is UART_DM_SR.
Also the msm_hs_request_clock_off() API is accessing wrong
register macro UARTDM_IMR instead of UART_DM_IMR.

This patch places the right macros at respective points.

CRs-Fixed: 583426
Change-Id: I0eb966adedc44b8e611da318b6d8f4a9279e95a7
Signed-off-by: Dilip Kota <c_dkota@codeaurora.org>