cxgb3i: suppot of different kernel page sizes

The default kernel pages supported are 4K, 8K, 16K, and 64K. Re-calculate
entries if PAGE_SIZE is not one of the defaults.

Signed-off-by: Karen Xie <kxie@chelsio.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>