tcsetattr on redox doesn't support anything other than TCSANOW

In sys_ioctl it only checks for the TCSETS (TCSANOW) ioctl kind, and not TCSETSW (TCSADRAIN, TCSETS + 1) or TCSETSF (TCSAFLUSH, TCSETS + 2). I'm not sure if it would be a really easy fix, since the TCSETS handling as is seems pretty rudimentary, but maybe it'd be possible to just forward all the variants to the TCSETS code.