powerpc: Fix doorbell type shift

doorbell type is defined as bits 32:36 so should be shifted by 63-36 =
27 rather than 28.

We never noticed this bug as we've only every used type PPC_DBELL = 0.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/dbell.h

@@ -18,7 +18,7 @@
 #include <asm/ppc-opcode.h>
 
 #define PPC_DBELL_MSG_BRDCAST	(0x04000000)
-#define PPC_DBELL_TYPE(x)	(((x) & 0xf) << 28)
+#define PPC_DBELL_TYPE(x)	(((x) & 0xf) << (63-36))
 enum ppc_dbell {
 	PPC_DBELL = 0,		/* doorbell */
 	PPC_DBELL_CRIT = 1,	/* critical doorbell */