m68k: Fix warnings with gcc 4.6

Most of the warnings seem to be related to using 'int' for size_t. Change
this and fix up the remaining warnings and problems. For bootm, the warning
was masked by others, and there is an actual bug in the code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/astro/mcf5373l/mcf5373l.c b/board/astro/mcf5373l/mcf5373l.c
index daba32c..7ec7cb3 100644
--- a/board/astro/mcf5373l/mcf5373l.c
+++ b/board/astro/mcf5373l/mcf5373l.c
@@ -79,7 +79,7 @@
 	 * (Do not rely on the SDCS register(s) being set to 0x00000000
 	 * during reset as stated in the data sheet.)
 	 */
-	return get_ram_size((unsigned long *)CONFIG_SYS_SDRAM_BASE,
+	return get_ram_size((long *)CONFIG_SYS_SDRAM_BASE,
 				0x80000000 - CONFIG_SYS_SDRAM_BASE);
 }