Build fails when PKG_ABI set

[ChristianMertes]

I'm building a kernel with a set PKG_ABI as in a custom suffix to differentiate the package and the kernel entry from the standard system kernels. Unfortunately, this suffix string (sbz in my case) shows up in the following code where an integer is expected and it's interpreted as a variable that was never declared. This usually goes unnoticed because PKG_ABI is set to 0 if it's unset.

./drivers/hv/hv.c: In function ‘hv_init’:
<command-line>:0:9: error: ‘sbz’ undeclared (first use in this function)
./drivers/hv/hv.c:225:81: note: in expansion of macro ‘PKG_ABI’
  hv_context.guestid = generate_guest_id(0x80 /*Canonical*/, LINUX_VERSION_CODE, PKG_ABI);
                                                                                 ^