Added *REG_BIT_MSK_AND_SET macros

Added CLR_REG_BIT_MSK_AND_SET and TOG_SET_REG_BIT_MSK_AND_SET because we
need version of CLR_REG_BIT_MSK and TOG_SET_REG_BIT_MSK that allow us to
OR in bits before the register is written.

Signed-off-by: George McCollister <george.mccollister@gmail.com>
Prevent RX_CTR and TX_CTR from being cleared

When writing the USB endpoint register, USB_EP_RX_CTR (bit 15) and
USB_EP_TX_CTR (bit 7) should be set to avoid inadvertently clearing
either bit.

Prior to this patch end points could indefinately stall if the hardware
changed these bits between the time they are read and when they were
written.

Signed-off-by: George McCollister <george.mccollister@gmail.com>