UBUNTU: [debian] derive indep_hdrs_pkg_name from src_pkg_name

This long-standing oversight in our debian rules hardcodes the string "linux"
instead of using the $(src_pkg_name) for just one of the generated .deb package
names: linux-headers-x.x.x-x.  Lets fix it in the generic branches
(T,X,Y,Z,unstable) so that we won't have to keep applying this patch to each of
the derivative/custom kernels.

-----8<-----

Ignore: yes
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Ben Romer <ben.romer@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

debian/rules.d/0-common-vars.mk

@@ -126,7 +126,7 @@ stampdir	:= $(CURDIR)/debian/stamps
 bin_pkg_name=linux-image-$(abi_release)
 extra_pkg_name=linux-image-extra-$(abi_release)
 hdrs_pkg_name=linux-headers-$(abi_release)
-indep_hdrs_pkg_name=linux-headers-$(abi_release)
+indep_hdrs_pkg_name=$(src_pkg_name)-headers-$(abi_release)
 
 #
 # The generation of content in the doc package depends on both 'AUTOBUILD=' and