xtensa: implement flush_icache_user_range

xtensa: implement flush_icache_user_range

The Xtensa implementation of flush_icache_range seems to be able to cope
with user addresses.  Just define flush_icache_user_range to
flush_icache_range.

[jcmvbkbc@gmail.com: fix flush_icache_user_range in noMMU configs]
Link: http://lkml.kernel.org/r/20200525221556.4270-1-jcmvbkbc@gmail.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Link: http://lkml.kernel.org/r/20200515143646.3857579-23-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>