mmc: block: add RPMB dependency

Prevent build error when CONFIG_RPMB=m and CONFIG_MMC_BLOCK=y by adding
a dependency to CONFIG_RPMB for CONFIG_MMC_BLOCK block so the RPMB
subsystem always is reachable if configured. This means that
CONFIG_MMC_BLOCK automatically becomes compiled as a module if
CONFIG_RPMB is compiled as a module. If CONFIG_RPMB isn't configured or
is configured as built-in, CONFIG_MMC_BLOCK will remain unchanged.

Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Fixes: 7852028a35f0 ("mmc: block: register RPMB partition with the RPMB subsystem")
Signed-off-by: Jens Wiklander <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/core/Kconfig

···
 config MMC_BLOCK
 	tristate "MMC block device driver"
 	depends on BLOCK
+	depends on RPMB || !RPMB
 	imply IOSCHED_BFQ
 	default y
 	help