[BOOTVID:PC98][PC98VID] Disable the text layer when setting mode (reactos#8539)

The previous approach was causing the contents of TVRAM to be visible after boot:
https://github.com/user-attachments/assets/df6d2782-4d54-41ab-b4c9-caeb170c4e1e

Fixes a regression introduced in 0fa4901.

CORE-17977

Author: disean

drivers/base/bootvid/i386/pc98/bootvid.c

@@ -219,6 +219,9 @@ InitializeDisplay(VOID)
     TextSync();
     TextSync();
 
+    /* Turn off the text layer */
+    WRITE_GDC1_COMMAND(GDC_COMMAND_STOP2);
+
     /* START */
     WRITE_GDC2_COMMAND(GDC_COMMAND_BCTRL_START);
 

win32ss/drivers/miniport/pc98vid/hardware.c

@@ -227,6 +227,9 @@ Pc98VidSetCurrentMode(
     TextSync();
     TextSync();
 
+    /* Turn off the text layer */
+    WRITE_GDC1_COMMAND(GDC_COMMAND_STOP2);
+
     /* START */
     WRITE_GDC2_COMMAND(GDC_COMMAND_BCTRL_START);