MMC core learns about SPI

Teach the MMC/SD/SDIO core about using SPI mode.

 - Use mmc_host_is_spi() so enumeration works through SPI signaling
   and protocols, not just the native versions.

 - Provide the SPI response type flags with each request issued,
   including requests from the new lock/unlock code.

 - Understand that cmd->resp[0] and mmc_get_status() results for SPI
   return different values than for "native" MMC/SD protocol; this
   affects resetting, checking card lock status, and some others.

 - Understand that some commands act a bit differently ... notably:
     * OP_COND command doesn't return the OCR
     * APP_CMD status doesn't have an R1_APP_CMD analogue

Those changes required some new and updated primitives:

 - Provide utilities to access two SPI-only requests, and one
   request that wasn't previously needed:
     * mmc_spi_read_ocr() ... SPI only
     * mmc_spi_set_crc() ... SPI only (override by module parm)
     * mmc_send_cid() ... for use without broadcast mode

 - Updated internal routines:
     * Previous mmc_send_csd() modified into mmc_send_cxd_native();
       it uses native "R2" responses, which include 16 bytes of data.
     * Previous mmc_send_ext_csd() becomes new mmc_send_cxd_data()
       helper for command-and-data access
     * Bugfix to that mmc_send_cxd_data() code:  dma-to-stack is
       unsafe/nonportable, so kmalloc a bounce buffer instead.

 - Modified mmc_send_ext_csd() now uses mmc_send_cxd_data() helper

 - Modified mmc_send_csd(), and new mmc_spi_send_cid(), routines use
   those helper routines based on whether they're native or SPI

The newest categories of cards supported by the MMC stack aren't expected
to work yet with SPI:  MMC or SD cards with over 4GB data, and SDIO.
All those cards support SPI mode, so eventually they should work too.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>