[e820mangler] Add missing CLC ins. for success path

The get_underlying_e820 function should return with CF unset on success.

Reported-by: Timothy Stack <tstack@vmware.com>
Signed-off-by: Marty Connor <mdc@etherboot.org>

src/arch/i386/firmware/pcbios/e820mangler.S

 	popw	%di
 	incw	%bx
 	movl	%edx, %eax
+	clc
 	ret
 2:	
 	/* If the requested region is earlier than the cached region,