target-arm: Do not reset sysregs marked as ALIAS

cp_reg_reset() is called from g_hash_table_foreach() which does not
define a specific ordering of the hash table iteration. Thus doing reset
for registers marked as ALIAS would give an ambiguous result when
resetvalue is different for original and alias registers. Exit
cp_reg_reset() early when passed an alias register. Then clean up alias
register definitions from needless resetvalue and resetfn.

In particular, this fixes a bug in the handling of the PMCR register,
which had different resetvalues for its 32 and 64-bit views.

Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
Message-id: 1434554713-10220-1-git-send-email-serge.fdrv@gmail.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index c9d2330..2f59058 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -1116,8 +1116,8 @@
  * old must have the OVERRIDE bit set.
  * ALIAS indicates that this register is an alias view of some underlying
  * state which is also visible via another register, and that the other
- * register is handling migration; registers marked ALIAS will not be migrated
- * but may have their state set by syncing of register state from KVM.
+ * register is handling migration and reset; registers marked ALIAS will not be
+ * migrated but may have their state set by syncing of register state from KVM.
  * NO_RAW indicates that this register has no underlying state and does not
  * support raw access for state saving/loading; it will not be used for either
  * migration or KVM state synchronization. (Typically this is for "registers"