[media] m88rs2000: fix sparse static warnings

fix the following warnings:
m88rs2000.c:300:16: warning: symbol 'm88rs2000_setup' was not declared. Should it be static?
m88rs2000.c:318:16: warning: symbol 'm88rs2000_shutdown' was not declared. Should it be static?
m88rs2000.c:328:16: warning: symbol 'fe_reset' was not declared. Should it be static?
m88rs2000.c:366:16: warning: symbol 'fe_trigger' was not declared. Should it be static?

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>