powerpc: Fix mktree build error on Mac OS X host

The mktree utility defines some variables as "uint", although this is not a
standard C type, and so cross-compiling on Mac OS X fails.  Change this to
"unsigned int".

Signed-off-by: Timur Tabi <timur@freescale.com>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>