i.MX6: Correct ANATOP_PFD (Phase Fractional Divider) register declarations

Some _CLKGATE_MASK and _FRAC_MASK macros were wrong for PFD_480
and the PFD_528 macros were missing.

Fortunately, the incorrect macros weren't being used.

Since both the PFD_480 and PFD_528 registers have the same
structure, and the fields are identical for [0..3] in bytes
[0..3], so a single set of macros will suffice.

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
i.MX6: Add convenience macros cpu_type(rev) and is_cpu_type(cpu)

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
i.MX6: Set and clear the gating bits for Phase Fractional Dividers

This addresses silicon errata ERR006282 as described in this
document:
	https://community.freescale.com/docs/DOC-94581

Also implemented in Freescale's 2009.08-based release:

	http://git.freescale.com/git/cgit.cgi/imx/uboot-imx.git/
	Commit id: b7c5badf94ffbe6cd0845efbb75e16e05e3af404

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>