mmc: rtsx_usb: Enable MMC_CAP_ERASE to allow erase/discard/trim requests

mmc: rtsx_usb: Enable MMC_CAP_ERASE to allow erase/discard/trim requests

BugLink: https://bugs.launchpad.net/bugs/1811337
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Michał Pecio <michal.pecio@gmail.com>
(cherry picked from commit 400fdb25c87431dd23194b5f6ec62ffae1b224ce)
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>