gpu mem bpf program - switch to LICENSE macro

Without this resulting .o is incorrectly formatted
and fails to load with newer bpfloader.

Bug: 190519702
Test: atest, TreeHugger - existing bpf programs load
  examination of bpfloader logs
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ie1a3ed0cdaebc533e4533ed5bfefd369ec2a87b3
Merged-In: Ie1a3ed0cdaebc533e4533ed5bfefd369ec2a87b3
diff --git a/services/gpuservice/bpfprogs/gpu_mem.c b/services/gpuservice/bpfprogs/gpu_mem.c
index c75213b..16e1e8a 100644
--- a/services/gpuservice/bpfprogs/gpu_mem.c
+++ b/services/gpuservice/bpfprogs/gpu_mem.c
@@ -72,4 +72,4 @@
     return 0;
 }
 
-char _license[] SEC("license") = "Apache 2.0";
+LICENSE("Apache 2.0");