ARM: OMAP2+: clock data: add DEFINE_STRUCT_CLK_FLAGS helper

DEFINE_STRUCT_CLK does not have the capability to set flags, define
DEFINE_STRUCT_CLK_FLAGS to handle flags. This is needed to add
SET_RATE_PARENT flag in statically defined lcd clock in am335x.

Signed-off-by: Afzal Mohammed <afzal@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>