input: qcom-hv-haptics: Update "get_fifo_length_us" with T_LRA_X

Update "get_fifo_length_us" function to support the T_LRA_X_2/4/8
periods. So that the FIFO mode can work for all T_LRA periods.

Change-Id: I5d6b2c95eff66cddcec9388082c4d540493f2c86
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>