x86: Re-enable PCAT timer 2 for beeping

While we don't want PCAT timers for timing, we want timer 2 so that we can
still make a beep. Re-purpose the PCAT driver for this, and enable it in
coreboot.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/include/asm/u-boot-x86.h

@@ -41,6 +41,7 @@ typedef void (timer_fnc_t) (void);
 int register_timer_isr (timer_fnc_t *isr_func);
 unsigned long get_tbclk_mhz(void);
 void timer_set_base(uint64_t base);
+int pcat_timer_init(void);
 
 /* Architecture specific - can be in arch/x86/cpu/, arch/x86/lib/, or $(BOARD)/ */
 int dram_init_f(void);