staging: et131x: Remove even more forward declarations

Moved functions in et131x.c file to remove the forward declarations of:

et1310_in_phy_coma
et1310_phy_access_mii_bit
et131x_phy_mii_read
et131x_mii_write
et131x_rx_dma_memory_free
Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>