Currently micd_dbtime can be set to 0 for default, 1 for 4 measurements,
or a greater than 16-bit value for 2 measurements. This patch simplifies
the symantics to 2 for 2 measurements, 4 for 4 measurements and any
other value for the default.

I am not super keen on changing the symantics of the pdata at this stage
in the drivers life, but acceptance of the DT binding for this field has
been made conditional on this happening.
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>