sdp: incorrect SDP_FMR_SIZE on 32-bit machines

sdp: incorrect SDP_FMR_SIZE on 32-bit machines

On 32-bit machines, sizeof (u64 *) is 4 bytes (size of a ***pointer***).
However, the max SDP FMR pool size should be PAGE_SIZE / sizeof(an mtt entry) --
and mtt entries are u64's (or __be64's).

This resulted in SDP requesting twice as many entries per pool on 32-bit machines
as could fit on a single page -- with the result that the fmr pool allocation failed
at driver startup.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>