isdn/capi: Make verbose reporting depend on capidrv

The Kconfig symbol ISDN_DRV_AVMB1_VERBOSE_REASON is only used for
capi_info2str(). That function is only used in capidrv.c. So setting it
without setting ISDN_CAPI_CAPIDRV is pointless. Make it depend on
ISDN_CAPI_CAPIDRV, rename it to ISDN_CAPI_CAPIDRV_VERBOSE and put its
entry after ISDN_CAPI_CAPIDRV's entry.

Since this symbol seems to be primarily used for debugging, keep it off
by default. By now the last users of capidrv hopefully know all they
need to know about the reasons for disconnecting.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>