RDMA/hfi1: Fix potential integer multiplication overflow errors

When multiplying of different types, an overflow is possible even when
storing the result in a larger type. This is because the conversion is
done after the multiplication. So arithmetic overflow and thus in
incorrect value is possible.

Correct an instance of this in the inter packet delay calculation.  Fix by
ensuring one of the operands is u64 which will promote the other to u64 as
well ensuring no overflow.

Cc: stable@vger.kernel.org
Fixes: 7724105 ("IB/hfi1: add driver files")
Link: https://lore.kernel.org/r/20220520183712.48973.29855.stgit@awfm-01.cornelisnetworks.com
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/hfi1/init.c

@@ -489,7 +489,7 @@ void set_link_ipg(struct hfi1_pportdata *ppd)
 	u16 shift, mult;
 	u64 src;
 	u32 current_egress_rate; /* Mbits /sec */
-	u32 max_pkt_time;
+	u64 max_pkt_time;
 	/*
 	 * max_pkt_time is the maximum packet egress time in units
 	 * of the fabric clock period 1/(805 MHz).