fbdev: clps711x-fb: Request memory region for MMIO

Use devm_platform_get_and_ioremap_resource() for resource 0 (the MMIO
control register range) instead of open-coding platform_get_resource()
and devm_ioremap() separately. The helper requests the memory region
before mapping it, which registers the range in /proc/iomem and prevents
another driver from mapping the same registers.

This makes resource 0 consistent with resource 1 (the framebuffer),
which already uses devm_platform_get_and_ioremap_resource().

Assisted-by: Claude:claude-sonnet-4-6
Signed-off-by: Amit Barzilai <amit.barzilai22@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>