enic: Fix 64 bit divide on 32bit system

Division of a 32 bit number by a 64 bit number causes the following link
error introduced by
7c2ce6e6 "enic: Add support for adaptive interrupt coalescing"

drivers/built-in.o: In function `enic_poll_msix':
enic_main.c:(.text+0x48710a): undefined reference to `__udivdi3'
make: *** [vmlinux] Error 1

Since numerator is 32 bit, convert denominator to 32 bit accordingly.

Fixes: 7c2ce6e6 ("enic: Add support for adaptive interrupt coalescing")
Reported-by: Jim Davis <jim.epost@gmail.com>
Cc: Christian Benvenuti <benve@cisco.com>
Cc: Sujith Sankar <ssujith@cisco.com>
Cc: Neel Patel <neepatel@cisco.com>
Signed-off-by: Govindarajulu Varadarajan <_govind@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>