Omap35xxPkg/Omap35xxTimerLib: Create a TimerConstructor in the TimerLib

This constructor should be explicitely called by the Sec or PrePi phase
to initialize the OMAP353x timers.

This function is a copy of the Timer initialization function in BeagleBoardPkg/Sec.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11988 6f19259b-4bc3-4df7-8a09-765794883524