net: stmmac: do not use a bitwise AND operator with a bool operand

Doing a bitwise AND between a bool and an int is generally not a good idea.
The bool will be promoted to an int with value 0 or 1,
the int is generally regarded as true with a non-zero value,
thus ANDing them has the potential to yield an undesired result.

This commit fixes the following smatch warnings:

drivers/net/ethernet/stmicro/stmmac/enh_desc.c:344 enh_desc_prepare_tx_desc() warn: maybe use && instead of &
drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c:337 dwmac4_rd_prepare_tx_desc() warn: maybe use && instead of &
drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c:380 dwmac4_rd_prepare_tso_tx_desc() warn: maybe use && instead of &

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>