Staging: rts5139: Fix Sparse Warning for Static Declarations in rts51x.c

This patch fixes the following sparse warning in rts51x.c

drivers/staging/rts5139/rts51x.c:218:5: warning: symbol 'rts51x_pre_reset' was not declared. Should it be static?
drivers/staging/rts5139/rts51x.c:229:5: warning: symbol 'rts51x_post_reset' was not declared. Should it be static?

Signed-off-by: Monam Agarwal <monamagarwal123@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>