Staging: fbtft: add declaration of non-static functions

This patch fixes these sparse warnings:
drivers/staging/fbtft/fbtft-sysfs.c:23:5: warning: symbol 'fbtft_gamma_parse_str' was not declared. Should it be static?
drivers/staging/fbtft/fbtft-sysfs.c:153:6: warning: symbol 'fbtft_expand_debug_value' was not declared. Should it be static?
drivers/staging/fbtft/fbtft-sysfs.c:209:6: warning: symbol 'fbtft_sysfs_init' was not declared. Should it be static?
drivers/staging/fbtft/fbtft-sysfs.c:216:6: warning: symbol 'fbtft_sysfs_exit' was not declared. Should it be static?
Signed-off-by: Peter Poklop <peter.poklop@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fbtft/fbtft-sysfs.c

 #include "fbtft.h"
-
+#include "internal.h"
 
 static int get_next_ulong(char **str_p, unsigned long *val, char *sep, int base)
 {