tests: net: ppp: Compile test with PPP statistics

Make sure the compilation is ok if PPP statistics is enabled.

This is related to commit 3e70425
("net: ppp: stats: Fix net_mgmt request handler format") which
was needed because earlier commit 5a9a39c
("net: mgmt: Convert the mgmt API to use 64-bit masks")
missed an compile problem because there was no compile test that
enabled CONFIG_NET_STATISTICS_PPP option.

Signed-off-by: Jukka Rissanen <[email protected]>

Author: jukkar

tests/net/ppp/driver/testcase.yaml

@@ -6,3 +6,8 @@ common:
 tests:
   net.ppp:
     min_ram: 21
+  net.ppp.statistics:
+    extra_args:
+      - CONFIG_NET_STATISTICS=y
+      - CONFIG_NET_STATISTICS_PPP=y
+      - CONFIG_NET_STATISTICS_USER_API=y