osmo-bts-xyz: include pcu_l1_if_phy.h in phy in l1_if code

The file pcu_l1_if_phy.h contains the function prototypes for the
implementations found in xyz_l1_if.c. Lets also include pcu_l1_if_phy.h
in the related .c files.

Change-Id: Id35ba473973108da4e36d5c6f2ca78da1225ae8b
Related: OS#5198
diff --git a/src/osmo-bts-litecell15/lc15_l1_if.c b/src/osmo-bts-litecell15/lc15_l1_if.c
index c1b9b71..053844f 100644
--- a/src/osmo-bts-litecell15/lc15_l1_if.c
+++ b/src/osmo-bts-litecell15/lc15_l1_if.c
@@ -34,6 +34,7 @@
 #include <lc15_l1_if.h>
 #include <gprs_debug.h>
 #include <pcu_l1_if.h>
+#include <pcu_l1_if_phy.h>
 #include <pdch.h>
 #include <bts.h>