runtime: simplify constant strings in asm

As of CL 163747, we can write arbitrary length strings
in assembly DATA instructions.

Make use of it here to improve readability.

Change-Id: I556279ca893f527874e3b26112c43573834ccd9c
Reviewed-on: https://go-review.googlesource.com/c/go/+/167386
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/asm_386.s

@@ -248,16 +248,8 @@ ok:
 	CALL	runtime·abort(SB)
 	RET
 
-DATA	bad_proc_msg<>+0x00(SB)/8, $"This pro"
-DATA	bad_proc_msg<>+0x08(SB)/8, $"gram can"
-DATA	bad_proc_msg<>+0x10(SB)/8, $" only be"
-DATA	bad_proc_msg<>+0x18(SB)/8, $" run on "
-DATA	bad_proc_msg<>+0x20(SB)/8, $"processo"
-DATA	bad_proc_msg<>+0x28(SB)/8, $"rs with "
-DATA	bad_proc_msg<>+0x30(SB)/8, $"MMX supp"
-DATA	bad_proc_msg<>+0x38(SB)/4, $"ort."
-DATA	bad_proc_msg<>+0x3c(SB)/1, $0xa
-GLOBL	bad_proc_msg<>(SB), RODATA, $0x3d
+DATA	bad_proc_msg<>+0x00(SB)/61, $"This program can only be run on processors with MMX support.\n"
+GLOBL	bad_proc_msg<>(SB), RODATA, $61
 
 DATA	runtime·mainPC+0(SB)/4,$runtime·main(SB)
 GLOBL	runtime·mainPC(SB),RODATA,$4

src/runtime/asm_amd64.s

@@ -1438,10 +1438,8 @@ flush:
 	MOVQ	96(SP), R15
 	JMP	ret
 
-DATA	debugCallFrameTooLarge<>+0x00(SB)/8, $"call fra"
-DATA	debugCallFrameTooLarge<>+0x08(SB)/8, $"me too l"
-DATA	debugCallFrameTooLarge<>+0x10(SB)/4, $"arge"
-GLOBL	debugCallFrameTooLarge<>(SB), RODATA, $0x14	// Size duplicated below
+DATA	debugCallFrameTooLarge<>+0x00(SB)/20, $"call frame too large"
+GLOBL	debugCallFrameTooLarge<>(SB), RODATA, $20	// Size duplicated below
 
 // debugCallV1 is the entry point for debugger-injected function
 // calls on running goroutines. It informs the runtime that a
@@ -1565,7 +1563,7 @@ good:
 	// The frame size is too large. Report the error.
 	MOVQ	$debugCallFrameTooLarge<>(SB), AX
 	MOVQ	AX, 0(SP)
-	MOVQ	$0x14, 8(SP)
+	MOVQ	$20, 8(SP) // length of debugCallFrameTooLarge string
 	MOVQ	$8, AX
 	BYTE	$0xcc
 	JMP	restore