hw/sd/sdcard: Allow user creation of eMMCs

hw/sd/sdcard: Allow user creation of eMMCs

For testing eMMC-specific functionality (such as handling boot
partitions), it would be very useful to attach them to generic VMs such
as x86_64 via the sdhci-pci device:
 ...
 -drive if=none,id=emmc-drive,file=emmc.img,format=raw \
 -device sdhci-pci \
 -device emmc,id=emmc0,drive=emmc-drive,boot-partition-size=1048576 \
 ...

While most eMMCs are soldered to boards, they can also be connected to
SD controllers with just a passive adapter, such as:
 https://docs.radxa.com/en/accessories/emmc-to-usd
 https://github.com/voltlog/emmc-wfbga153-microsd

The only change necessary to make the options above work is to avoid
disabling user_creatable, so do that. The SDHCI-PCI driver in the Linux
kernel already supports this just fine.

Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
Acked-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20241015135649.4189256-1-jlu@pengutronix.de>

Enable user-instantiation so that eMMCs can be created for PCI-attached
SD/MMC host controllers (such as sdhci-pci) on virt machines, for QA
purposes for the eMMC model itself and for complex firmware/OS
integrations using the upcoming RPMB partition support.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Message-ID: <e515cc80de261ff03b3141724298f20313259a85.1762261430.git.jan.kiszka@siemens.com>
Tested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>