openrisc: entry: Fix delay slot detection

Use execption SR stored in pt_regs for detection, the current SR is not
correct as the handler is running after return from exception.

Also, The code that checks for a delay slot uses a flag bitmask and then
wants to check if the result is not zero.  The test it implemented was
wrong.

Correct it by changing the test to check result against non zero.

Signed-off-by: Stafford Horne <shorne@gmail.com>

arch/openrisc/kernel/entry.S

@@ -258,9 +258,9 @@ EXCEPTION_ENTRY(_data_page_fault_handler)
 
 #else
 
-	l.mfspr r6,r0,SPR_SR               // SR
+	l.lwz   r6,PT_SR(r3)               // SR
 	l.andi  r6,r6,SPR_SR_DSX           // check for delay slot exception
-	l.sfeqi r6,0x1                     // exception happened in delay slot
+	l.sfne  r6,r0                      // exception happened in delay slot
 	l.bnf   7f
 	 l.lwz  r6,PT_PC(r3)               // address of an offending insn