media: Make HAVE_FM_RADIO play nice with OMAP_ENHANCEMENT

OMAP_ENHANCEMENT devices can use CM's FM app (and stack)
without using HAVE_FM_RADIO, but the volume controls are lost.

If the target device's master volume affects FM, using
BOARD_HAVE_FM_RADIO is sufficient.
However, if a specific FM volume control is necessary,
HAVE_FM_RADIO needs to be used (and the volume functions
implemented in that device's HAL)

Change-Id: I00c46727a6f09cdd0cc11265a0a94a5a5aa63721