omapfb: dispc: Various typo fixes

- value and register offset was swapped in a dispc write
- DISPC_CONTROL register was used instead of DISPC_SYSCONFIG
- FIFO size bit field had incorrect length for OMAP3

Fixed-by: arun <arunedarath@mistralsolutions.com>
Fixed-by: Kalle Jokiniemi <ext-kalle.jokiniemi@nokia.com>
Fixed-by: Andrzej Zaborowski <balrog@zabor.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Imre Deak <imre.deak@nokia.com>