af-main: add RDEPENDS on bash

Currently, we get a file-rdeps QA warning because afm-install has a
/bin/bash shebang line but does not RDEPENDS on bash. We could also use
/bin/sh instead, but I'm not sure if we have some bashisms built-in to
the script. For now, add RDEPENDS to fix the warning.

Change-Id: I368da5e9e5c2d57d7bc2a1b674eb84c1147be5c1
Signed-off-by: Martin Kelly <mkelly@xevo.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/10221
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>