libpayload/libc/time: Add an arch_ndelay()

Replace _delay with an arch_ndelay(). This way each arch can setup their
own delay mechanism.

BUG=b:109749762
TEST=Verified delay's still work on grunt.

Change-Id: I552eb30984f9c21e92dffc9d7b36873e9e2e4ac5
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-on: https://review.coreboot.org/28243
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Richard Spiegel <richard.spiegel@silverbackltd.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

payloads/libpayload/libc/time.c

@@ -158,52 +158,14 @@ int gettimeofday(struct timeval *tv, void *tz)
 	return 0;
 }
 
-static inline void _delay(uint64_t delta)
+__attribute__((weak))
+void arch_ndelay(uint64_t ns)
 {
+	uint64_t delta = ns * timer_hz() / NSECS_PER_SEC;
 	uint64_t start = timer_raw_value();
 	while (timer_raw_value() - start < delta) ;
 }
 
-/**
- * Delay for a specified number of nanoseconds.
- *
- * @param n Number of nanoseconds to delay for.
- */
-void ndelay(unsigned int n)
-{
-	_delay((uint64_t)n * timer_hz() / 1000000000);
-}
-
-/**
- * Delay for a specified number of microseconds.
- *
- * @param n Number of microseconds to delay for.
- */
-void udelay(unsigned int n)
-{
-	_delay((uint64_t)n * timer_hz() / 1000000);
-}
-
-/**
- * Delay for a specified number of milliseconds.
- *
- * @param m Number of milliseconds to delay for.
- */
-void mdelay(unsigned int m)
-{
-	_delay((uint64_t)m * timer_hz() / 1000);
-}
-
-/**
- * Delay for a specified number of seconds.
- *
- * @param s Number of seconds to delay for.
- */
-void delay(unsigned int s)
-{
-	_delay((uint64_t)s * timer_hz());
-}
-
 u64 timer_us(u64 base)
 {
 	static u64 hz;