x86/purgatory: Make functions and variables static

Sparse emits several 'symbol not declared' warnings for various
functions and variables.

Add static keyword to functions and variables which have file scope
only.
Signed-off-by: Tobin C. Harding <me@tobin.cc>
Link: http://lkml.kernel.org/r/1487545956-2547-2-git-send-email-me@tobin.ccSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/purgatory/purgatory.c

@@ -18,11 +18,11 @@ struct sha_region {
 	unsigned long len;
 };
 
-unsigned long backup_dest = 0;
-unsigned long backup_src = 0;
-unsigned long backup_sz = 0;
+static unsigned long backup_dest;
+static unsigned long backup_src;
+static unsigned long backup_sz;
 
-u8 sha256_digest[SHA256_DIGEST_SIZE] = { 0 };
+static u8 sha256_digest[SHA256_DIGEST_SIZE] = { 0 };
 
 struct sha_region sha_regions[16] = {};
 
@@ -39,7 +39,7 @@ static int copy_backup_region(void)
 	return 0;
 }
 
-int verify_sha256_digest(void)
+static int verify_sha256_digest(void)
 {
 	struct sha_region *ptr, *end;
 	u8 digest[SHA256_DIGEST_SIZE];