staging: sm750fb: Rename vScreen to v_screen in lynxfb_crtc

staging: sm750fb: Rename vScreen to v_screen in lynxfb_crtc

The struct lynxfb_crtc has a member named vScreen. This name is
CamelCase and is frowned upon. This commit renames it to v_screen
and makes the necessary changes for the module to build.

This change also fixes the following checkpatch CHECKs:

CHECK: Avoid CamelCase: <vScreen>
454: FILE: sm750.c:454:
+		memset_io(crtc->vScreen, 0x0, crtc->vidmem_size);

CHECK: Avoid CamelCase: <vScreen>
136: FILE: sm750.h:136:
+	unsigned char __iomem *vScreen; /* virtual address of on_screen */

Signed-off-by: Benjamin Philip <benjamin.philip495@gmail.com>
Link: https://lore.kernel.org/r/52db14bfc2f39e246aed7fdf866845a72e503b36.1627413010.git.benjamin.philip495@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>