arm64: mv: a37x0_gpio: Set the memory to SHAREABLE

Since r349596 the syscon driver will map the memory. Since the gpio/pinctrl
controller wants it too set it to SHAREABLE.
This fix the gpio controller for attaching and so consumer can use it.
Now the sdhci_xenon driver can detect presence of an sdcard and attach
the mmc driver.

MFC after: 1 week