gpib: Fix fluke driver s390 compile issue

gpib: Fix fluke driver s390 compile issue

The following errors were reported for a s390 randconfig build
of the fluke gpib driver:

>> drivers/gpib/eastwood/fluke_gpib.c:1002:23: error: call to undeclared function 'ioremap'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    1002 |         nec_priv->mmiobase = ioremap(e_priv->gpib_iomem_res->start,
         |                              ^
>> drivers/gpib/eastwood/fluke_gpib.c:1002:21: error: incompatible integer to pointer conversion assigning to 'void *' from 'int' [-Wint-conversion]
    1002 |         nec_priv->mmiobase = ioremap(e_priv->gpib_iomem_res->start,
         |                            ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    1003 |                                      resource_size(e_priv->gpib_iomem_res));
         |                                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/gpib/eastwood/fluke_gpib.c:1036:33: error: incompatible integer to pointer conversion assigning to 'void *' from 'int' [-Wint-conversion]
    1036 |         e_priv->write_transfer_counter = ioremap(e_priv->write_transfer_counter_res->start,
         |                                        ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    1037 |                                                  resource_size(e_priv->write_transfer_counter_res));
         |                                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Add HAS_IOMEM dependency to Kconfig for fluke driver option

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601221748.AFAqHieJ-lkp@intel.com/
Fixes: baf8855c9160 ("staging: gpib: fix address space mixup")
Cc: stable <stable@kernel.org>
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Link: https://patch.msgid.link/20260202094755.4259-1-dpenkler@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>