Step towards modularizing the Flattened Device Tree code.

Define attributes for each of the specific device bindings: clock,
dai, dma, gpio, i2c, iommu, mbox, mmc_pwrseq, phy, power, power domain,
pwm, regulator, reset controller, spi, system controller, pin
controller. Include these support files only if either a provider
or consumer with one of these attributes is present in the kernel
config.

Add the necessary attributes to the device / attach declarations for
each provider and consumer.

There are some bindings that are consumed by generic code (iommu, pinctrl,
power, power domain). Provide weak stubs for these routines to handle
situations where there is no provider.

No actual code changed; NFCI.

i.mx6sx CPU support in the CCM module: the clock tree si different from
the i.mx6q
- move i.mx6q-specific functions and data to imx6_clk.c
- add i.mx6sx specific imx6sx_clk.c
- add a imx6sxccm device

branches: 1.2.4;
drm: Use CPPFLAGS.drmkms in all local drm drivers too.

This way we don't pollute the NetBSD kernel namespace with all the
Linux compat shim definitions needed to build drm, except for the
local drm drivers that need the API.

branches: 1.1.2;
Tidyup the i.MX SoC support by

- Moving the FDTised code to sys/arch/arm/nxp to match the
sys/arch/{cpu}/{vendor} convention
- FDTise some more drivers
- Secure Non-Volatile Storage
- watchdog driver
- On chip OTP
- Match fsl,imx6dl
- Add some more drivers to GENERIC that will be supported by i.MX 6
boards