soc: imx: gpcv2: make pgc driver more generic for other i.MX platforms

i.MX8MQ and i.MX8MM share same gpc module with i.MX7D, they
can reuse gpcv2 pgc driver for power domain control, this
patch renames all functions and structure definitions started
with "imx7" to "imx", and use .data in imx_gpcv2_dt_ids[] to
pass platform specific power domain data for power domain
driver, thus make gpcv2 pgc driver more generic for i.MX
platforms.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>