MIPS: ftrace: Declare ftrace_get_parent_ra_addr() as static

Declare ftrace_get_parent_ra_addr() as static to suppress clang
compiler warning that 'no previous prototype'. This function is
not intended to be called from other parts.

Fix follow error with clang-19:

arch/mips/kernel/ftrace.c:251:15: error: no previous prototype for function 'ftrace_get_parent_ra_addr' [-Werror,-Wmissing-prototypes]
251 | unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
| ^
arch/mips/kernel/ftrace.c:251:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
251 | unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
| ^
| static
1 error generated.

Signed-off-by: WangYuli <[e-mail]>
Acked-by: Masami Hiramatsu (Google) <[e-mail]>
Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/kernel/ftrace.c

···
 #define S_R_SP	(0xafb0 << 16)	/* s{d,w} R, offset(sp) */
 #define OFFSET_MASK	0xffff	/* stack offset range: 0 ~ PT_SIZE */
 
-unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
+static unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
 		old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
 {
 	unsigned long sp, ip, tmp;