This option enables the workaround for the 753970 PL310 (r3p0) erratum.

Under some condition the effect of cache sync operation on
the store buffer still remains when the operation completes.
This means that the store buffer is always asked to drain and
this prevents it from merging any further writes. The workaround
is to replace the normal offset of cache sync operation (0x730)
by another offset targeting an unmapped PL310 register 0x740.
This has the same effect as the cache sync operation: store buffer
drain and waiting for all buffers empty.