tsc2101-alsa build fixes

Partial build fixes for tsc2101 audio.  It still won't link though,
it needs undefined omap_tsc2101_{read,write}() functions to access
chip registers ... and requires that e.g. tsc2102 audio isn't also
configured (they use the same exported McBSP DMA functions, which
likewise prevent use with EAC).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>