bnx2x: Combine get_pcie_width and get_pcie_speed

The functions bnx2x_get_pcie_width() and bnx2x_get_pcie_speed() were
combined into bnx2x_get_pcie_width_speed() so that there is only
1 PCI read to PCICFG_OFFSET + PCICFG_LINK_CONTROL rather then 2 reads.

Signed-off-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>