khugepaged: arm64: Don't collapse MTE enabled VMAs

copy_user_highpage() will do memory allocation if there are saved tags for
the destination page, and the page is missing tag storage.

After commit a349d72f ("mm/pgtable: add rcu_read_lock() and
rcu_read_unlock()s"), collapse_huge_page() calls
__collapse_huge_page_copy() -> .. -> copy_user_highpage() with the RCU lock
held, which means that copy_user_highpage() can only allocate memory using
GFP_ATOMIC or equivalent.

Get around this by refusing to collapse pages into a transparent huge page
if the VMA is MTE-enabled.