drivers/misc/ti-st: remove sparse warnings

remove sparse warnings by assigning right storage specifiers to functions and
also clean-up the declarations in the include/linux/ti_wilink_st.h

Signed-off-by: Pavan Savoy <pavan_savoy@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>