sparc64: Fix build errors with gcc-4.6.0

Most of the warnings emitted (we fail arch/sparc file
builds with -Werror) were legitimate but harmless, however
one case (n2_pcr_write) was a genuine bug.

Based almost entirely upon a patch by Sam Ravnborg.

Reported-by: Dennis Gilmore <dennis@ausil.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/pcr.c

@@ -81,7 +81,7 @@ static void n2_pcr_write(u64 val)
 	unsigned long ret;
 
 	ret = sun4v_niagara2_setperf(HV_N2_PERF_SPARC_CTL, val);
-	if (val != HV_EOK)
+	if (ret != HV_EOK)
 		write_pcr(val);
 }