staging: wfx: make methods 'wfx_get_ps_timeout' and 'wfx_update_pm' static

staging: wfx: make methods 'wfx_get_ps_timeout' and 'wfx_update_pm' static

Add "static" for local methods wfx_get_ps_timeout() and
wfx_update_pm() to address following sparse warnings.

wfx/sta.c:203:5: warning: symbol 'wfx_get_ps_timeout' was not declared. Should it be static?
wfx/sta.c:233:5: warning: symbol 'wfx_update_pm' was not declared. Should it be static?

Signed-off-by: Julius Hemanth Pitti <juliushemanth@gmail.com>
Link: https://lore.kernel.org/r/1591737854-11855-1-git-send-email-juliushemanth@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>