tridentfb: fix hang on Blade3D with CONFIG_CC_OPTIMIZE_FOR_SIZE

When the kernel is compiled with -Os (CONFIG_CC_OPTIMIZE_FOR_SIZE), tridentfb
hangs the machine upon load with Blade3D cards unless acceleration is disabled.

This is caused by memcpy() which copies data byte-by-byte (rep movsb) when
compiled with -Os. The card does not like that - it requires 32-bit access.

Use iowrite_32() instead.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>