[ARM] 3293/1: don't invalidate the whole I-cache with xscale_coherent_user_range

Patch from Nicolas Pitre

The mini I-cache issue is valid only for kernel space since debuggers
would not fly if they used user space addresses for their stubs.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>