x86: provide readq()/writeq() on 32-bit too, complete

if HAVE_READQ/HAVE_WRITEQ are defined, the full range of readq/writeq
APIs has to be provided to drivers:

 drivers/infiniband/hw/amso1100/c2.c: In function 'c2_tx_ring_alloc':
 drivers/infiniband/hw/amso1100/c2.c:133: error: implicit declaration of function '__raw_writeq'

So provide them on 32-bit as well. Also, map all the APIs to the
strongest ordering variant. It's way too easy to mess such details
up in drivers and the difference between "memory" and "" constrained
asm() constructs is in the noise range.

Signed-off-by: Ingo Molnar <mingo@elte.hu>