unicore32 framebuffer fix: get videomemory by __get_free_pages() and make it floatable

1. get videomemory by __get_free_pages() in fb-puv3.c
2. remove resource reservation for old fixed UNIGFX_MMAP & UVC_MMAP space
3. remove unused macros: PKUNTIY_UNIGFX_MMAP_BASE, PKUNITY_UNIGFX_MMAP_SIZE,
	PKUNITY_UVC_MMAP_BASE, PKUNITY_UVC_MMAP_SIZE and KUSER_UNIGFX_BASE
4. remove unused header linux/vmalloc.h in fb-puv3.h

Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Acked-by: Arnd Bergmann <arnd@arndb.de>