drivers: base: remove check for callback in coredump_store()

The check for the .coredump() callback in coredump_store() is
redundant. It is already assured the device driver implements
the callback upon creating the coredump sysfs entry.

Signed-off-by: Arend van Spriel <aspriel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>