Clear LCD cursor state on reset

Data after the palette member isn't cleared on reset, but that's needed for
the cursor state. Especially when switching from CX II emulation to classic
emulation, the cursor remains enabled while the registers are inaccessible.

core/lcd.h

@@ -17,7 +17,6 @@ typedef struct lcd_state {
     uint32_t control;
     uint8_t int_mask;
     uint8_t int_status;
-    uint16_t palette[256];
     uint8_t cursor_ram[64*64/4]; // 64x64 2bpp cursor
     uint8_t cursor_control;
     uint8_t cursor_config;
@@ -26,6 +25,8 @@ typedef struct lcd_state {
     uint16_t cursor_clip;
     uint8_t cursor_int_mask;
     uint8_t cursor_int_status;
+    // Below here isn't zeroed in lcd_reset
+    uint16_t palette[256];
 } lcd_state;
 
 void lcd_draw_frame(uint8_t *buffer);