OMAPDSS: HDMI: fix hdmi_wait_for_bit_change

hdmi_wait_for_bit_change() has two issues:

The register index was passed as u16, even if the register index may be
u32. Fix the index to u32.

The function was copied from wait_for_bit_change() which waits for a
single bit to change, but the hdmi version was changed to wait for a bit
field. This change was not done correctly.

The function is supposed to return the (last) value of the bit field,
but it returned !val in case of timeout. This was correct for the single
bit version, but not for the hdmi version. Fix the function to return
the actual value in the register.

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