These variables:
* vga_can_do_color
* vgacon_text_mode_force
* vga_font_is_default
* vga_hardscroll_enabled
* vga_hardscroll_user_enable
* vga_init_done
* vga_is_gfx
* vga_palette_blanked
* vga_512_chars
are used exclusively as a boolean value, so make them really a bool.
Remove also useless "? true : false".
__read_mostly annotations removed too as they obfuscate the code and I
doubt they improve anything measurable given the variables are used
from .con_scroll, .con_startup and such.