galaxys2: add AGPS psc field

The GPS chipset used in the phone can use the Psc value for AGPS.
Rename field in AGpsRefLocationCellID struct and add a new define.

Credit to Qaweck from xda-developers forum for finding the meaning
of the field.

Change-Id: Ib917c3b0ebf3c4b0a683fc993ff41521a01b32d4