dts: arm: nxp: nxp_lpc55s6x: Remove wrong comment
dts: arm: nxp: nxp_lpc55s6x: Remove wrong comment

sram4 is not connected to USB. The following sram area that is not part
of the device tree is. So the comment is removed with this commit.

Signed-off-by: Christian Taedcke <5dfb12f5b8690cb9c18e955016e7e3173b81d0d8@lemonbeat.com>

finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr