[profile] Standardise return type of profile_timestamp()

All consumers of profile_timestamp() currently treat the value as an
unsigned long.  Only the elapsed number of ticks is ever relevant: the
absolute value of the timestamp is not used.  Profiling is used to
measure short durations that are generally fewer than a million CPU
cycles, for which an unsigned long is easily large enough.

Standardise the return type of profile_timestamp() as unsigned long
across all CPU architectures.  This allows 32-bit architectures such
as i386 and riscv32 to omit all logic associated with retrieving the
upper 32 bits of the 64-bit hardware counter, which simplifies the
code and allows riscv32 and riscv64 to share the same implementation.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/riscv64/include/bits/profile.h

@@ -1,28 +0,0 @@
-#ifndef _BITS_PROFILE_H
-#define _BITS_PROFILE_H
-
-/** @file
- *
- * Profiling
- *
- */
-
-FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
-
-#include <stdint.h>
-
-/**
- * Get profiling timestamp
- *
- * @ret timestamp	Timestamp
- */
-static inline __attribute__ (( always_inline )) uint64_t
-profile_timestamp ( void ) {
-	uint64_t cycles;
-
-	/* Read timestamp counter */
-	__asm__ __volatile__ ( "rdcycle %0" : "=r" ( cycles ) );
-	return cycles;
-}
-
-#endif /* _BITS_PROFILE_H */