bnx2x: Remove the init_dmae field from bp

Moved the dmae_command from the heap to the stack.  This will save 56
bytes per bnx2x structure.   As a side benefit, we can also reduce the
time the dmae_mutex is held.  This is because do we not need to hold
this mutex when setting up the dmae command.  The memory where is dmae
command is stored is not a shared resource and doesn not need to be
protected.

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>