lib: posix: pthread_common: Fix potential integer overflow issue
lib: posix: pthread_common: Fix potential integer overflow issue

Fix potential overflow of interger expression for by fixing
variable type to s64_t.

CID: 185275

Signed-off-by: Ramakrishna Pallala <8cb5df094165bcc31e7d772ccd8d87d8c4d8f761@intel.com>

explora26/zephyr,ldts/zephyr,Vudentz/zephyr,galak/zephyr,ldts/zephyr,mbolivar/zephyr,kraj/zephyr,nashif/zephyr,galak/zephyr,mbolivar/zephyr,zephyriot/zephyr,finikorg/zephyr,ldts/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,ldts/zephyr,zephyriot/zephyr,nashif/zephyr,ldts/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,mbolivar/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,nashif/zephyr,kraj/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,punitvara/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,mbolivar/zephyr,finikorg/zephyr,Vudentz/zephyr,explora26/zephyr,kraj/zephyr,mbolivar/zephyr,kraj/zephyr,galak/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,zephyriot/zephyr,kraj/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,nashif/zephyr