MX51: removed warnings for the mx51evk

The patch removes warnings at compile time and provides
some cleanup code:
- Removed comment on NAND (not yet supported) from lowlevel_init.S
- Removed NFMS bit definition from imx-regs.h
  The bit is only related to MX.25/35 and can lead to confusion
- Moved is_soc_rev() to soc specific code (removed from mx51evk.c)

Signed-off-by: Stefano Babic <sbabic@denx.de>
diff --git a/include/asm-arm/arch-mx51/sys_proto.h b/include/asm-arm/arch-mx51/sys_proto.h
new file mode 100644
index 0000000..bf500a8
--- /dev/null
+++ b/include/asm-arm/arch-mx51/sys_proto.h
@@ -0,0 +1,30 @@
+/*
+ * (C) Copyright 2009
+ * Stefano Babic, DENX Software Engineering, sbabic@denx.de.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef _SYS_PROTO_H_
+#define _SYS_PROTO_H_
+
+u32 get_cpu_rev(void);
+#define is_soc_rev(rev)	((get_cpu_rev() & 0xFF) - rev)
+
+#endif