[PATCH] ppc32: fix CONFIG_TASK_SIZE handling on 44x

This patch fixed CONFIG_TASK_SIZE handling on 44x.  Currently head_44x.S
hardcodes 0x80000000, which breaks if user chooses to change TASK_SIZE
(e.g.  for 3G user-space).  Tested on Ocotea in 3G/1G configuration.

Signed-off-by: Eugene Surovegin <ebs@ebshome.net>
Signed-off-by: Matt Porter <mporter@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>