s390/dasd: add missing MODULE_DESCRIPTION() macros

With ARCH=s390, make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/s390/block/dasd_diag_mod.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/s390/block/dasd_eckd_mod.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/s390/block/dasd_fba_mod.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://lore.kernel.org/r/20240715112434.2111291-2-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>