x86: remove superfluous initialisation in boot code.

In arch/x86/boot/compressed/misc.c, the variable vidmem is
the only variable that ends up in de data segment. It's also
superfluous, because the first thing the code does is:

	if (RM_SCREEN_INFO.orig_video_mode == 7) {
		vidmem = (char *) 0xb0000;
		vidport = 0x3b4;
	} else {
		vidmem = (char *) 0xb8000;
		vidport = 0x3d4;
	}

This patch removes the initialisation.

Signed-off-by: Ingo Molnar <mingo@elte.hu>