fbdev: hgafb: Request memory region before ioremap

The driver calls ioremap() on the HGA video memory at 0xb0000 without
first reserving the physical address range. This leaves the kernel
resource tree incomplete and can cause silent conflicts with other
drivers claiming the same range.

Add a devm_request_mem_region() call before ioremap() in
hga_card_detect() to reserve the memory region.

Signed-off-by: Hardik Phalet <hardik.phalet@pm.me>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Helge Deller <deller@gmx.de>