IB/qib: rename BITS_PER_PAGE to RVT_BITS_PER_PAGE

We get this build warning on arm64

drivers/infiniband/hw/qib/qib_qp.c:44:0: error: "BITS_PER_PAGE" redefined [-Werror]
 #define BITS_PER_PAGE           (PAGE_SIZE*BITS_PER_BYTE)

This is fixed upstream in commit 898fa52b ("IB/qib: Remove qpn, qp tables and
related variables from qib"), which does a lot of other things as well.

Instead, I just backport the rename of the local BITS_PER_PAGE definition to
RVT_BITS_PER_PAGE.

The driver first showed up in linux-2.6.35, and the fixup should still apply
to that. The upstream fix went into v4.6, so we could apply this workaround
to both 3.18 and 4.4.

Fixes: f931551b ("IB/qib: Add new qib driver for QLogic PCIe InfiniBand adapters")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>