8250: use correct value for PORT_BRCM_TRUMANAGE
When backporting commit
ebebd49a8eab ('8250/16?50: Add support for
Broadcom TruManage redirected serial port') I took the next
available port type number for PORT_BRCM_TRUMANAGE (22).
However, the 8250 port type numbers are exposed to userland through
the TIOC{G,S}SERIAL ioctls and so must remain stable. Redefine
PORT_BRCM_TRUMANAGE as 25, matching mainline as of commit
85f024401bf807.
This leaves port types 22-24 within the valid range for 8250 but not
implemented there. Change serial8250_verify_port() to specifically
reject these and change serial8250_type() to return "unknown" for them
(though I'm not sure why it would ever see them).
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>