staging: gpib: Avoid unused variable warnings

staging: gpib: Avoid unused variable warnings

This addresses warnings produced by make W=1 with the configuration
parameter CONFIG_GPIB_PCMCIA=y

cb7210/cb7210.c:1251:28: warning: variable 'dev' set but not used [-Wunused-but-set-variable]
cb7210/cb7210.c:1250:31: warning: variable 'handle' set but not used [-Wunused-but-set-variable]

Remove the declarations and assignments of the unused variables.

Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Link: https://lore.kernel.org/r/20250427093123.18565-1-dpenkler@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>