ARM: 6386/1: flush_ptrace_access: invalidate correct I-cache alias

copy_to_user_page can be used by access_process_vm to write to an
executable page of a process using a mapping acquired by kmap.
For systems with I-cache aliasing, flushing the I-cache using the
Kernel mapping may leave stale data in the I-cache if the user
mapping is of a different colour.

This patch introduces a flush_icache_alias function to flush.c,
which calls flush_icache_range with a mapping of the specified
colour. flush_ptrace_access is then modified to call this new
function instead of coherent_kern_range in the case of an aliasing
I-cache and a non-aliasing D-cache.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>