Rename %eflags to %rflags.

EFLAGS is a subregister of RFLAGS. For consistency with GPRs where we
use the 64-bit names to refer to the registers, use the 64-bit name for
RFLAGS as well.

lib/cretonne/src/isa/intel/binemit.rs

@@ -257,7 +257,7 @@ fn icc2opc(cond: IntCC) -> u16 {
 
 /// Get the low 4 bits of an opcode for a floating point condition code.
 ///
-/// The ucomiss/ucomisd instructions set the EFLAGS bits CF/PF/CF like this:
+/// The ucomiss/ucomisd instructions set the FLAGS bits CF/PF/CF like this:
 ///
 ///    ZPC OSA
 /// UN 111 000