meta-samsung: split tuna machine into maguro/toro/toroplus

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-asus: split grouper machine into grouper/tilapia

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-samsung: don't explicitly check in a common script for tuna machine

Checking for tuna machine in a script common for more than one machine prevents
MACHINEOVERRIDES from being used.

Signed-off-by: Simon Busch <morphis@gravedo.de>