OMAP: DSS2: improve clock debugfs output

OMAP4 has clocks set up in a bit interesting way, causing, for example,
the DSS's "ick" to be called "dss_fck".

This patch changes the debugfs output to show both the DSS's name for
the clock (ie. basically the clock alias), and the real name from the
clock struct.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>