msm: sensor: actuator: avoid accessing out of bound memory

Issue:
When total_steps is updated, after that, copy_from_user
fails with an error, then, i2c_reg_tbl is not allocated.
In this case, when calling msm_actuator_parse_i2c_params,
it lead to out-of-bound memory write.

Fix:
1) Assign total_steps to zero when error from copying.
2) Add NULL pointer check for i2c tbl.

CRs-Fixed: 2111672
Change-Id: Ib9dcb182356e2df8078c131edfd0791fa95a35e0
Signed-off-by: Haibin Liu <haibinl@codeaurora.org>