ARM: sun6i: Add clock support

This patch adds the basic clocks support for the Allwinner A31 (sun6i)
processor. This code will not been compiled until the build is hooked
up in a later patch. It has been split out to keep the patches manageable.

This includes changes from the following commits from u-boot-sunxi:

a92051b ARM: sunxi: Add sun6i clock controller structure
1f72c6f ARM: sun6i: Setup the UART0 clocks
5f2e712 ARM: sunxi: Enable pll6 by default on all models
2be2f2a ARM: sunxi-mmc: Add mmc support for sun6i / A31
12e1633 ARM: sun6i: Add initial clock setup for SPL
1a9c9c6 ARM: sunxi: Split clock code into common, sun4i and sun6i code
0b194ee ARM: sun6i: Properly setup the PLL LDO in clock_init_safe
b54c626 sunxi: avoid sr32 for APB1 clock setup.
68fe29c sunxi: remove magic numbers from clock_get_pll{5,6}
c89867d sunxi: clocks: clock_get_pll5 prototype and coding style
501ab1e ARM: sunxi: Fix sun6i PLL6 settings
37f669b ARM: sunxi: Fix macro names for mmc and uart reset offsets
61de1e6 ARM: sunxi: Correct comment for MBUS1 register in sun6i clock definitions

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
[wens@csie.org: styling fixes reported by checkpatch.pl]
[wens@csie.org: drop unsupported SPL code block and unused gpio.h header]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Cc: Tom Cubie <Mr.hipboi@gmail.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>