s390/configs//zfcpdump_defconfig: Remove CONFIG_MEMSTICK

This config option is completely irrelevant for zfcpdump and
unfortunately causes a kernel panic on recent kernels in
"mspro_block_init()/driver_register()".

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>