csky: drop asm/gpio.h wrapper

The asm/gpio.h header is gone now that all architectures just use
gpiolib, and so the redirect is no longer valid.

Acked-by: Guo Ren <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>

arch/csky/include/asm/Kbuild

···
 # SPDX-License-Identifier: GPL-2.0
 generic-y += asm-offsets.h
 generic-y += extable.h
-generic-y += gpio.h
 generic-y += kvm_para.h
 generic-y += mcs_spinlock.h
 generic-y += qrwlock.h