n1sdp: Correct ternary operator statement

The last ternary operator (for speed == 1333) was useless because it did
not differentiate between true or false. If more values are needed maybe
a switch-case would be more appropriate.

Change-Id: I43392fa4ac9c2487e523cbec5c1de37ef8c3f11b
Signed-off-by: Raphael Gault <raphael.gault@arm.com>