hw/misc: Mark most objects as "common" code to speed up compilation a litte bit

hw/misc: Mark most objects as "common" code to speed up compilation a litte bit

Most of the code in hw/misc/ does not directly depend on CPU-specific
code. Mark it as "common" so that the code can be shared between e.g.
qemu-system-arm and qemu-system-aarch64, or between the various mips
flavours, instead of recompiling it for each and every target again
and again.

Signed-off-by: Thomas Huth <[email protected]>
Message-Id: <20190902162638[email protected]>
Signed-off-by: Alex Bennée <[email protected]>