APFv6.1: introduce alloc_xmit opcode

Before:
   text    data     bss     dec     hex filename
   3032       0       0    3032     bd8 apf_interpreter.armt.o
   4639       0       0    4639    121f apf_interpreter.arm.o
   4740       0       0    4740    1284 apf_interpreter.aarch64.o
   5899       0       0    5899    170b apf_interpreter.x86.o
   5849       0       0    5849    16d9 apf_interpreter.x86-64.o
After:
   text    data     bss     dec     hex filename
   3128       0       0    3128     c38 apf_interpreter.armt.o
   4777       0       0    4777    12a9 apf_interpreter.arm.o
   4856       0       0    4856    12f8 apf_interpreter.aarch64.o
   6029       0       0    6029    178d apf_interpreter.x86.o
   5999       0       0    5999    176f apf_interpreter.x86-64.o

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <[email protected]>
Change-Id: Iad932c46fe1757092468282f50bf50e11183d518
3 files changed