iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()

iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()

iter->copy_mc is only used with a bvec iterator and only by
dump_emit_page() in fs/coredump.c so rather than handle this in
memcpy_from_iter_mc() where it is checked repeatedly by _copy_from_iter()
and copy_page_from_iter_atomic(),

Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
cc: Alexander Viro <[email protected]>
cc: Jens Axboe <[email protected]>
cc: Christoph Hellwig <[email protected]>
cc: Christian Brauner <[email protected]>
cc: Matthew Wilcox <[email protected]>
cc: Linus Torvalds <[email protected]>
cc: David Laight <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>