mm/early_ioremap.c: remove redundant early_ioremap_shutdown()

mm/early_ioremap.c: remove redundant early_ioremap_shutdown()

early_ioremap_reset() reserved a weak function so that architectures can
provide a specific cleanup.  Now no architectures use it, remove this
redundant function.

Link: https://lkml.kernel.org/r/20210901082917.399953-1-o451686892@gmail.com
Signed-off-by: Weizhao Ouyang <o451686892@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>