um: Fix -Wmissing-prototypes warnings for __vdso_*

The VDSO functions are defined as globals and intended to be called
from userspace. Let's just workaround the -Wmissing-prototypes warnings
by declaring them locally.

This will address below -Wmissing-prototypes warnings:

arch/x86/um/vdso/um_vdso.c:16:5: warning: no previous prototype for ‘__vdso_clock_gettime’ [-Wmissing-prototypes]
arch/x86/um/vdso/um_vdso.c:30:5: warning: no previous prototype for ‘__vdso_gettimeofday’ [-Wmissing-prototypes]
arch/x86/um/vdso/um_vdso.c:44:21: warning: no previous prototype for ‘__vdso_time’ [-Wmissing-prototypes]
arch/x86/um/vdso/um_vdso.c:57:1: warning: no previous prototype for ‘__vdso_getcpu’ [-Wmissing-prototypes]

While at it, also fix the "WARNING: Prefer 'unsigned int *' to bare
use of 'unsigned *'" checkpatch warning.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/x86/um/vdso/um_vdso.c

@@ -13,6 +13,12 @@
 #include <linux/getcpu.h>
 #include <asm/unistd.h>
 
+/* workaround for -Wmissing-prototypes warnings */
+int __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts);
+int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz);
+__kernel_old_time_t __vdso_time(__kernel_old_time_t *t);
+long __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused);
+
 int __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
 {
 	long ret;
@@ -54,7 +60,7 @@ __kernel_old_time_t __vdso_time(__kernel_old_time_t *t)
 __kernel_old_time_t time(__kernel_old_time_t *t) __attribute__((weak, alias("__vdso_time")));
 
 long
-__vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
+__vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused)
 {
 	/*
 	 * UML does not support SMP, we can cheat here. :)
@@ -68,5 +74,5 @@ __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
 	return 0;
 }
 
-long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
+long getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *tcache)
 	__attribute__((weak, alias("__vdso_getcpu")));