Add generic driver for on-chip SRAM

These patches add support to configure on-chip SRAM via device-tree
node or platform data and to obtain the resulting genalloc pool from
the physical address or a phandle pointing at the device tree node.
This allows drivers to allocate SRAM with the genalloc API without
hard-coding the genalloc pool pointer.

The on-chip SRAM on i.MX53 and i.MX6q can be registered via device tree
and changed to use the simple generic SRAM driver:

                ocram: ocram@00900000 {
                        compatible = "fsl,imx-ocram", "sram";
                        reg = <0x00900000 0x3f000>;
                };

A driver that needs to allocate SRAM buffers, like the video processing
unit on i.MX53, can retrieve the genalloc pool from a phandle in the
device tree using of_get_named_gen_pool(node, "iram", 0) from patch 1:

                vpu@63ff4000 {
                        /* ... */
                        iram = <&ocram>;
                };

Changes since v5:
 - Addressed Paul Gortmaker's comments, merging the clock patch
   into the SRAM driver patch.
 - Hard coded the allocation granularity to 512 bytes and dropped
   Matt Porter's patch for now. Whether or not this should be
   configured in the device tree could use further discussion.
 - Added a coda driver patch to use the genalloc API and, again,
   the i.MX53/i.MX6 device tree patch to show the whole picture.

regards
Philipp

---
 Documentation/devicetree/bindings/misc/sram.txt |   17 ++++
 arch/arm/boot/dts/imx53.dtsi                    |    5 +
 arch/arm/boot/dts/imx6q.dtsi                    |    6 ++
 drivers/media/platform/Kconfig                  |    3 +-
 drivers/media/platform/coda.c                   |   47 ++++++---
 drivers/misc/Kconfig                            |    9 ++
 drivers/misc/Makefile                           |    1 +
 drivers/misc/sram.c                             |  121 +++++++++++++++++++++++
 include/linux/genalloc.h                        |   14 +++
 lib/genalloc.c                                  |   67 +++++++++++++
 10 files changed, 274 insertions(+), 16 deletions(-)