msm: qpnp-haptic: Update function declarations

The header file currently has incorrect function declaration when
CONFIG_QPNP_HAPTIC is disabled and set to be compiled or set
as a module. Declare the functions static and inline them.

CRs-fixed: 1058405
Change-Id: I69b7e5542f561735ed044bdaf49f855b57777c84
Signed-off-by: Clyde Byrd III <cbyrd@codeaurora.org>