drivers: usb_dc_mcux: Use CONFIG_USB_DC_NXP_LPCIP3511 define

Use CONFIG_USB_DC_NXP_LPCIP3511 instead of FSL_FEATURE_USB_USB_RAM
as the behaviour variation is based on the SDK driver used and not
if the SoC has a dedicated USB SRAM.

Signed-off-by: Mahesh Mahadevan <mahesh.mahadevan@nxp.com>