bus: add driver for IMX AIPSTZ bridge

The secure AHB to IP Slave (AIPSTZ) bus bridge provides access control
configurations meant to restrict access to certain peripherals.
Some of the configurations include:

	1) Marking masters as trusted for R/W. Based on this
	(and the configuration of the accessed peripheral), the bridge
	may choose to abort the R/W transactions issued by certain
	masters.

	2) Allowing/disallowing write accesses to peripherals.

Add driver for this IP. Since there's currently no framework for
access controllers (and since there's currently no need for having
flexibility w.r.t the configurations) all this driver does is it
applies a relaxed, "default" configuration, in which all masters
are trusted for R/W.

Note that some instances of this IP (e.g: AIPSTZ5 on i.MX8MP) may be tied
to a power domain and may lose their configuration when the domain is
powered off. This is why the configuration has to be restored when the
domain is powered on.

Co-developed-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/bus/Kconfig

@@ -87,6 +87,12 @@ config HISILICON_LPC
 	  Driver to enable I/O access to devices attached to the Low Pin
 	  Count bus on the HiSilicon Hip06/7 SoC.
 
+config IMX_AIPSTZ
+	tristate "Support for IMX Secure AHB to IP Slave bus (AIPSTZ) bridge"
+	depends on ARCH_MXC
+	help
+	  Enable support for IMX AIPSTZ bridge.
+
 config IMX_WEIM
 	bool "Freescale EIM DRIVER"
 	depends on ARCH_MXC || COMPILE_TEST