blktap2: use abort() instead of custom crash

blktap2: use abort() instead of custom crash

Instead of trying to write a snippet of code that crashes the process
just use abort() directly. This is to fix the build on clang which
detects that the snippet of code will crash and fails to compile. At
the same time removed extraneous whitespace in the macro.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>