cpu/x86/tsc: remove conditional compilation

The delay_tsc.c compilation unit used the C preprocessor
to conditionally compile different code paths. Instead of
guarding large blocks of code allow the compiler to optimize
out unreachable code.

Change-Id: I660c21d6f4099b0d7aefa84b14f1e68d6fd732c3
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/14302
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Andrey Petrov <andrey.petrov@intel.com>
diff --git a/src/cpu/x86/tsc/delay_tsc.c b/src/cpu/x86/tsc/delay_tsc.c
index 439b477..6120b88 100644
--- a/src/cpu/x86/tsc/delay_tsc.c
+++ b/src/cpu/x86/tsc/delay_tsc.c
@@ -9,12 +9,6 @@
 
 static unsigned long clocks_per_usec CAR_GLOBAL;
 
-#if CONFIG_TSC_CONSTANT_RATE
-static unsigned long calibrate_tsc(void)
-{
-	return tsc_freq_mhz();
-}
-#else /* CONFIG_TSC_CONSTANT_RATE */
 #define CLOCK_TICK_RATE	1193180U /* Underlying HZ */
 
 /* ------ Calibrate the TSC -------
@@ -28,7 +22,7 @@
 #define CALIBRATE_INTERVAL ((2*CLOCK_TICK_RATE)/1000) /* 2ms */
 #define CALIBRATE_DIVISOR  (2*1000) /* 2ms / 2000 == 1usec */
 
-static unsigned long long calibrate_tsc(void)
+static unsigned long calibrate_tsc_with_pit(void)
 {
 	/* Set the Gate high, disable speaker */
 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
@@ -89,7 +83,13 @@
 	return 0;
 }
 
-#endif /* CONFIG_TSC_CONSTANT_RATE */
+static unsigned long calibrate_tsc(void)
+{
+	if (IS_ENABLED(CONFIG_TSC_CONSTANT_RATE))
+		return tsc_freq_mhz();
+	else
+		return calibrate_tsc_with_pit();
+}
 
 void init_timer(void)
 {