Fixes gcc '-Wunused-but-set-variable' warning:

drivers/misc/eeprom/at25.c: In function 'at25_remove':
drivers/misc/eeprom/at25.c:384:20: warning:
 variable 'at25' set but not used [-Wunused-but-set-variable]

Since commit 96d08fb4 ("eeprom: at25: use devm_nvmem_register()"),
at25_remove is do nothing, so can be removed.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>