Now that qualcommax exists as a target and dependencies have been updated
let move ipq807x support to subtarget of qualcommax.
This is mostly copy/paste with the exception of having to update SSDK and
NSS-DP to use CONFIG_TARGET_SUBTARGET.
This is a preparation for later addition of IPQ60xx and IPQ50xx support.
Signed-off-by: Robert Marko <robimarko@gmail.com>
