printk: add CONFIG_PRINTK dependency for netconsole

printk: add CONFIG_PRINTK dependency for netconsole

The 'select PRINTK_EXECUTION_CTX' line now causes a harmless warning
when NETCONSOLE_DYNAMIC is enabled but PRINTK is not:

WARNING: unmet direct dependencies detected for PRINTK_EXECUTION_CTX
  Depends on [n]: PRINTK [=n]
  Selected by [y]:
  - NETCONSOLE_DYNAMIC [=y] && NETDEVICES [=y] && NET_CORE [=y] && NETCONSOLE [=y] && SYSFS [=y] && CONFIGFS_FS [=y] && (NETCONSOLE [=y]!=y [=y] || CONFIGFS_FS [=y]!=m [=m])

In that configuration, the netconsole driver is useless anyway, so
avoid this with an added dependency that prevents CONFIG_NETCONSOLE
to be enabled without CONFIG_PRINTK.

Fixes: 60325c27d3cf ("printk: Add execution context (task name/CPU) to printk_info")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260213074431.1729627-1-arnd@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>