Documentation: mount_api: change kernel log wording

Documentation: mount_api: change kernel log wording

Change wording to say that messages are logged to the kernel log
buffer instead of to dmesg. dmesg is just one program that can
print the kernel log buffer.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20201202012409.19194-1-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>