arm64: Add memcpy_{from, to}io() and memset_io() helpers

arm64: Add memcpy_{from, to}io() and memset_io() helpers

Provide optimized memcpy_{from,to}io() and memset_io(). This is required
when moving large amount of data to and from IO regions such as IP
registers or accessing memory mapped flashes.

Code is borrowed from Linux Kernel v5.4.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>