layerscape/armv8_64b: enable DEBUG_INFO_REDUCED

layerscape/armv8_64b: enable DEBUG_INFO_REDUCED

We currently enable DEBUG_INFO_REDUCED for all targets via the generic
kernel config. There is only one subtarget, layerscape/armv8_64b, that
overrides this setting. As there is no explanation for this in the
commit message that introduced this, and question to its author went
unanswered, let's simply drop this symbol from the subtarget config.
This way, we have consistency across the tree, and we do not have to
introduce a special case when moving this symbol to an OpenWrt kernel
config option.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>