Blackfin: gptimers: add enable/disable by timer id

The API is geared around timer ids, except for the act of enabling
and disabling timers. So add a small helper to fill out the gap.

Signed-off-by: Mike Frysinger <[e-mail]>

arch/blackfin/include/asm/gptimers.h

···
 uint32_t get_gptimer_status(unsigned int group);
 void     set_gptimer_status(unsigned int group, uint32_t value);
 
+static inline void enable_gptimer(unsigned int timer_id)
+{
+	enable_gptimers(1 << timer_id);
+}
+
+static inline void disable_gptimer(unsigned int timer_id)
+{
+	disable_gptimers(1 << timer_id);
+}
+
 /*
  * All Blackfin system MMRs are padded to 32bits even if the register
  * itself is only 16bits.  So use a helper macro to streamline this.