OMAP3: Clock: Added IDLEST definitions for SGX

Added definitions for OMAP3430ES2_ST_SGX_SHIFT and OMAP3430ES2_ST_SGX_MASK
as these were missing.

Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>