configs/imx6-sabreauto: Add openssl for kernel build

Select BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL in order to fix
the following build error:

scripts/Makefile.host:90: recipe for target 'scripts/extract-cert' failed
make[2]: *** [scripts/extract-cert] Error 1
make[2]: *** Waiting for unfinished jobs....

Fixes: https://gitlab.com/buildroot.org/buildroot/-/jobs/332655822



Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>