msm: sensor: actuator: add null pointer check for i2c array

Issue:
i2c_reg_tbl may be null under error condition when set param.
then, other actuator function still may use the i2c_reg_tbl as null.
Fix:
1) the assignment total_steps follow on kmalloc buffer.
2) Add NULL pointer check for i2c tbl.

CRs-Fixed: 2152401
Change-Id: Ieec3d88e6dae0177787da0906f53d59ac4f5a624
Signed-off-by: Haibin Liu <haibinl@codeaurora.org>