Skip PDCH activation if the GPRS mode is 'none' at:
* TCH/F_PDCH init after OML Enable (dyn_pdch_init())
* after TCH/F_PDCH is released, in TCH/F mode
* in the T3111 error timer callback after a TCH/F_PDCH was released in error
state
Assert the GPRS mode in rsl_ipacc_pdch_activate() to make sure all callers
check the GPRS mode.
Closes: OS#1765
Change-Id: I970e5f9dbcb1c625209e914a4c7696294ed34e62