x86, setup: mark %esi as clobbered in E820 BIOS call

Jordan Hargrave diagnosed a BIOS clobbering %esi in the E820 call.
That particular BIOS has been fixed, but there is a possibility that
this is responsible for other occasional reports of early boot
failure, and it does not hurt to add %esi to the clobbers.

-stable candidate patch.

Cc: Justin Forbes <jmforbes@linuxtx.org>
Signed-off-by: Michael K Johnson <johnsonm@rpath.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: stable@kernel.org

arch/x86/boot/memory.c

@@ -27,13 +27,14 @@ static int detect_memory_e820(void)
 	do {
 		size = sizeof(struct e820entry);
 
-		/* Important: %edx is clobbered by some BIOSes,
-		   so it must be either used for the error output
+		/* Important: %edx and %esi are clobbered by some BIOSes,
+		   so they must be either used for the error output
 		   or explicitly marked clobbered. */
 		asm("int $0x15; setc %0"
 		    : "=d" (err), "+b" (next), "=a" (id), "+c" (size),
 		      "=m" (*desc)
-		    : "D" (desc), "d" (SMAP), "a" (0xe820));
+		    : "D" (desc), "d" (SMAP), "a" (0xe820)
+		    : "esi");
 
 		/* BIOSes which terminate the chain with CF = 1 as opposed
 		   to %ebx = 0 don't always report the SMAP signature on