input: qcom-hv-haptics: update drive waveform data format

Use 2's complement data format for driving pattern waveform because
the pattern/FIFO samples used in the driver are all having unsigned
data type.

Change-Id: Ib0f7c1c7fe272068177237821debbd3cc1ad4ec8
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>