target-ppc: Init dcache and icache size for e500 user mode

commit f7aa558396dd0f6b7a2b22c05cb503c655854102 pulled the dcache and icache
line size initialization inside of a '#if !defined(CONFIG_USER_ONLY)' block.
This is not correct because instructions like 'dcbz' need the dcache size
initialized even for user mode.

Signed-off-by: Meador Inge <meadori@codesourcery.com>
Cc: Varun Sethi <Varun.Sethi@freescale.com>
[AF: Simplify #ifdefs by using cache line size 32 for *-user as before]
Suggested-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
