[AVR] Add FeatureEIJMPCALL to FamilyAVR6

This feature was probably missed when adding FamilyAVR6, but should
definitely be there. I checked all four devices in the AVR6 family and
they all support eijmp/eicall.

Found while working on https://reviews.llvm.org/D137572.

Differential Revision: https://reviews.llvm.org/D137573

Author: aykevl

llvm/lib/Target/AVR/AVRDevices.td

@@ -184,7 +184,7 @@ def FamilyAVR5 : Family<"avr5",
 
 def FamilyAVR51 : Family<"avr51", [FamilyAVR5, FeatureELPM, FeatureELPMX]>;
 
-def FamilyAVR6 : Family<"avr6", [FamilyAVR51]>;
+def FamilyAVR6 : Family<"avr6", [FamilyAVR51, FeatureEIJMPCALL]>;
 
 def FamilyTiny
     : Family<"avrtiny",