stmmac: pci: allocate memory resources dynamically

Instead of using global variables we are going to use dynamically allocated
memory. It allows to append a support of more than one ethernet adapter which
might have different settings simultaniously.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>