ltq-vmmc: fix unknown type name errors

ltq-vmmc: fix unknown type name errors

Include missing header "drv_vmmc_api.h" to fix the compilation errors.

Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/18744
Signed-off-by: Robert Marko <robimarko@gmail.com>
(cherry picked from commit 1f909e9f6d839939c2c7e6f212077d3fc0a265e3)
Signed-off-by: Nora Matthias Schiffer <neocturne@universe-factory.net>
Link: https://github.com/openwrt/openwrt/pull/20440
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>