mmc: dw_mmc: Add support for 64-bit IDMAC

mmc: dw_mmc: Add support for 64-bit IDMAC

Some DW MMC blocks (e.g. those on modern Exynos chips) support 64-bit
DMA addressing mode. 64-bit DW MMC variants differ from their 32-bit
counterparts:
  - the register layout is a bit different (because there are additional
    IDMAC registers present for storing upper part of 64-bit addresses)
  - DMA descriptor structure is bigger and different from 32-bit one

Introduce all necessary changes to enable support for 64-bit DMA capable
DW MMC blocks. Next changes were made:

  1. Check which DMA address mode is supported in current IP-core
     version. HCON register (bit 27) indicates whether it's 32-bit or
     64-bit addressing. Add boolean .dma_64bit_address field to struct
     dwmci_host and store the result there. dwmci_init_dma() function is
     introduced for doing so, which is called on driver's init.

  2. Add 64-bit DMA descriptor (struct dwmci_idmac64) and use it in
     dwmci_prepare_desc() in case if .dma_64bit_address field is true.
     A new dwmci_set_idma_desc64() function was added for populating that
     descriptor.

  3. Add registers for 64-bit DMA capable blocks. To make the access to
     IDMAC registers universal between 32-bit / 64-bit cases, a new
     struct dwmci_idmac_regs (and corresponding host->regs field) was
     introduced, which abstracts the hardware by being set to
     appropriate offset constants on init. All direct calls to IDMAC
     registers were correspondingly replaced by accessing host->regs.

  4. Allocate and use 64-bit DMA descriptors buffer in case when IDMAC
     is 64-bit capable. Extract all the code (except for the IDMAC
     descriptors buffer allocation) from dwmci_send_cmd() to
     dwmci_send_cmd_common(), so that it's possible to keep IDMAC
     buffer (either 32-bit or 64-bit) on stack during send_cmd routine.

The insights for this implementation were taken from Linux kernel DW MMC
driver.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>