Main Conformance: Update SIN,COS error bounds

Large input values to SIN or COS can lead to
proportionately large errors in the angle and
so in the SIN or COS result.

Change-Id: Ibc0d8f4f1db27b8c8855c48a238040442c14ef71
Signed-off-by: Dominic Symes <dominic.symes@arm.com>