arch/x86: Make sure compiler knows we're stopping in hlt()

Currently, static analyzers don't recognize that hlt() doesn't return,
so they show errors like uninitialized variables assuming that it does
return.  This takes care of that problem.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: Ia2325700b10fe1f89d749edfe5aee72b47d02f2e
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56978
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/arch/x86/include/arch/hlt.h

@@ -3,9 +3,10 @@
 #ifndef ARCH_HLT_H
 #define ARCH_HLT_H
 
-static __always_inline void hlt(void)
+static __noreturn __always_inline void hlt(void)
 {
-	asm("hlt");
+	while (1)
+		asm("hlt");
 }
 
 #endif /* ARCH_HLT_H */