caif: Use UTILITY_NAME_LENGTH instead of hard-coding 16

UTILITY_NAME_LENGTH is 16. So better use the former when defining the
'utility_name' array. This makes the intent clearer when it is used around
line 260.

While at it, declare variable in reverse xmas tree style.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/8c1160501f69b64bb2d45ce9f26f746eec80ac77.1711787352.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Jakub Kicinski <kuba@kernel.org>