input: pmw3610: run the whole init with spi clock on

Move the pmw3610_spi_clk_on and pmw3610_spi_clk_off calls so that the
"on" call is before the first write. The datasheet calls for doing this
before any write operations, though some writes seems to work without
this in place, other seems to behave erroneously.

The non static functions do it on their own as they can be called
separately.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>