cmd/compile: soften test for 74788

We now (as of CL 678620) use float registers other than X0 for copying.

Change-Id: Ifdecd5df7519663742eed0f292c98453754d4b25
Reviewed-on: https://go-review.googlesource.com/c/go/+/695275
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Jorropo <[email protected]>

Author: randall77

test/codegen/issue74788.go

@@ -7,11 +7,11 @@
 package codegen
 
 func fa(a [2]int) (r [2]int) {
-	// amd64:1`MOVUPS[^,]+, X0$`,1`MOVUPS\sX0,[^\n]+$`
+	// amd64:1`MOVUPS[^,]+, X[0-9]+$`,1`MOVUPS\sX[0-9]+,[^\n]+$`
 	return a
 }
 
 func fb(a [4]int) (r [4]int) {
-	// amd64:2`MOVUPS[^,]+, X0$`,2`MOVUPS\sX0,[^\n]+$`
+	// amd64:2`MOVUPS[^,]+, X[0-9]+$`,2`MOVUPS\sX[0-9]+,[^\n]+$`
 	return a
 }