net: ksz884x: remove unused change variable

clang with W=1 reports
drivers/net/ethernet/micrel/ksz884x.c:3216:6: error: variable
  'change' set but not used [-Werror,-Wunused-but-set-variable]
        int change = 0;
            ^
This variable is not used so remove it.

Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230329125929.1808420-1-trix@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>