video: ARM CLCD: fix dma allocation size

This patch forces the frambuffer size to be aligned on kernel pages.

During the board startup, the splash screed did appear;
the "ts_test" program or our application were not able to start.

The following error message was reported:
error: failed to map framebuffer device to memory.
LinuxFB: driver cannot connect

The issue was discovered, on the LPC32xx platform, during the migration
of the LCD definition from the board file to the device tree.

Signed-off-by: Liam Beguin <lbeguin@tycoint.com>
Signed-off-by: Sylvain Lemieux <slemieux@tycoint.com>
Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>