qmsi: rtc: Use locking to guard critical section

Guard critical section of the driver API, so that
multiple simultaneous calls from tasks/fibers wont
corrupt the driver state.

The locking mechanism is by default disabled in the
build. To enable it, the following flag needs to be defined:

CONFIG_RTC_QMSI_API_REENTRANCY

Jira: ZEP-412

Change-Id: I430ebc07bf3277e5a5961cb6278c5500cd1e139b
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
Signed-off-by: Kuo-Lang Tseng <kuo-lang.tseng@intel.com>