hw/sd/sdcard: Basis for eMMC support

hw/sd/sdcard: Basis for eMMC support

Since eMMC are soldered on boards, it is not user-creatable.

RCA register is initialized to 0x0001, per spec v4.3,
chapter 8.5 "RCA register":

  The default value of the RCA register is 0x0001.
  The value 0x0000 is reserved to set all cards into
  the Stand-by State with CMD7.

The CSD register is very similar to SD one, except
the version announced is v4.3.

eMMC CID register is slightly different from SD:
- One extra PNM (5 -> 6)
- MDT is only 1 byte (2 -> 1).

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Cédric Le Goater <clg@redhat.com>
Message-Id: <20240712162719.88165-2-philmd@linaro.org>