sh: Track the uncached mapping size.

This provides a variable for tracking the uncached mapping size, and uses
it for pretty printing the uncached lowmem range. Beyond this, we'll also
be building on top of this for figuring out from where the remainder of
P2 becomes usable when constructing unrelated mappings.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/include/asm/system.h

@@ -137,6 +137,7 @@ extern unsigned int instruction_size(unsigned int insn);
 #endif
 
 extern unsigned long cached_to_uncached;
+extern unsigned long uncached_size;
 
 extern struct dentry *sh_debugfs_root;