mm/mremap: move remap_is_valid() into check_prep_vma()

mm/mremap: move remap_is_valid() into check_prep_vma()

Group parameter check logic together, moving check_mremap_params() next to
it.

This puts all such checks into a single place, and invokes them early so
we can simply bail out as soon as we are aware that a condition is not
met.

No functional change intended.

Link: https://lkml.kernel.org/r/4d0669c23531629d8ead42aa701c6237bd6bf012.1752770784.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>