staging: rtl8187se: Fix warning symbol should be static

This patch solves some sparse warnings about "symbol [...] was not
declared. Should it be static?" by including the correct header files.

Signed-off-by: Jonas Hahnfeld <hahnjo@hahnjo.de>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>