sparc64: don't treat 64-bit syscall return codes as 32-bit

When checking a system call return code for an error,
linux_sparc_syscall was sign-extending the lower 32-bit value and
comparing it to -ERESTART_RESTARTBLOCK. lseek can return valid return
codes whose lower 32-bits alone would indicate a failure (such as 4G-1).
Use the whole 64-bit value to check for errors. Only the 32-bit path
should sign extend the lower 32-bit value.

Signed-off-by: Dave Kleikamp <[e-mail]>
Acked-by: Bob Picco <[e-mail]>
Acked-by: Allen Pais <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: [e-mail]
Signed-off-by: David S. Miller <[e-mail]>

arch/sparc/kernel/syscalls.S

···
 	 mov	%i0, %l5				! IEU1
 5:	call	%l7					! CTI	Group brk forced
 	 srl	%i5, 0, %o5				! IEU1
-	ba,a,pt	%xcc, 3f
+	ba,pt	%xcc, 3f
+	 sra	%o0, 0, %o0
 
 	/* Linux native system calls enter here... */
 	.align	32
···
 3:	stx	%o0, [%sp + PTREGS_OFF + PT_V9_I0]
 ret_sys_call:
 	ldx	[%sp + PTREGS_OFF + PT_V9_TSTATE], %g3
-	sra	%o0, 0, %o0
 	mov	%ulo(TSTATE_XCARRY | TSTATE_ICARRY), %g2
 	sllx	%g2, 32, %g2