qemu: Add LEON2 support

This commit adds LEON2 support for SPARC architecture of QEMU.  It
consists of the following four patches:

 - 0001 is taken from github.com/AdaCore/qemu as is. The url is
   AdaCore/qemu@9d94f48

 - 0002 is to fix the build failure caused by 0001. Because the patch
   above (0001) depends on some other commits in the AdaCore repo.

 - 0003 is for a bug we found. I should have reported to AdaCore but
   haven't yet.

 - 0004 is a fix needed to rebase on top of v4.2.  It is for
   transaction based ptimer API introduced by
   qemu/qemu@78b6eaa

Signed-off-by: Yasushi SHOJI <[email protected]>

Author: yashi