libbpf: Use only 2 components in soversion, matching package name

Debian policy says the package name must change when the soname
changes.  We don't expect the ABI to change in a stable update,
so use only 2 components in both.

debian/changelog

@@ -2,6 +2,8 @@ linux (4.19.37-4) UNRELEASED; urgency=medium
 
   * libbpf: Fix various build bugs:
     - Drop unnecessary changes from "libbpf: add SONAME to shared object"
+    - libbpf: Use only 2 components in soversion, matching package name
+      (Closes: #929187)
 
  -- Ben Hutchings <ben@decadent.org.uk>  Sun, 19 May 2019 00:04:16 +0100
 

debian/patches/bugfix/all/libbpf-add-soname-to-shared-object.patch

@@ -29,7 +29,7 @@ Signed-off-by: Hilko Bengen <bengen@debian.org>
  N		=
  
 -LIBBPF_VERSION = $(BPF_VERSION).$(BPF_PATCHLEVEL).$(BPF_EXTRAVERSION)
-+LIBBPF_VERSION = $(shell make --no-print-directory -sC ../../.. kernelversion)
++LIBBPF_VERSION = $(shell make --no-print-directory -sC ../../.. kernelversion | cut -d. -f1,2)
  
  # Set compile option CFLAGS
  ifdef EXTRA_CFLAGS