OMAPDSS: DISPC: do not lose taps selection

Move taps selection logic before scaling check, so 3- of 5-tap always
get selected, no metter whether we do scaling or not.

Change-Id: I284b29933ca9fd69ae2088f279554dab9a66542c
Signed-off-by: Sergiy Kibrik <sergiy.kibrik@globallogic.com>