net: mctp: fix typo in comment

Correct a typo in af_mctp.c: "fist" -> "first".

Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Acked-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://patch.msgid.link/20250905165006.3032472-1-alok.a.tiwari@oracle.com


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