[U-Boot] MX6q SPI refactoring and related patches

[Eric Nelson]

I'm about to send an updated set of patches for mxc_spi re-factoring
and the related cleanup stemming from the discussions in
	http://lists.denx.de/pipermail/u-boot/2012-January/116816.html

These are split into multiple patch sets as suggested by Dirk:
	http://lists.denx.de/pipermail/u-boot/2012-January/116865.html

Because these are all re-sends, I'm tagging them as "V6" as requested
by Jason:
	http://lists.denx.de/pipermail/u-boot/2012-January/116894.html

I'm also including a "PART #" to make it clear which patches are
grouped together.

-- Part 1 will contain basic support for translating between
    ordinal GPIO numbers and port:index forms.
    It is required for parts 2, 4, and 5

-- Part 2 (3 patches) re-factors mxc_spi by moving register
    declarations into their arch-specific headers. This changed from
    the previous submission by using GPIO_NUMBER() instead of the
    undefined IMX_GPIO_NR().
	http://lists.denx.de/pipermail/u-boot/2012-January/116901.html

-- Part 3 (2 patches) allows a board to define default values
    for SPI ROM bus and chip-selects and add some documentation for the same.
    I believe these have already been approved by Mike Frysinger.

-- Part 4 defines defaults for the mx6qsabrelite board. Note
    that this is slightly different from previous submission by also
    changing a reference to GPIO_NUMBER(3,19) to use the new default
    value (CONFIG_SF_DEFAULT_CS).

-- Part 5 conditionally defines a configuration for use in
    booting and saving environment to SPI flash instead of SD card
    to make it easier to switch between them.