math64, timers: Fix 32bit mul_u64_u32_shr() and friends

math64, timers: Fix 32bit mul_u64_u32_shr() and friends

It turns out that while GCC-4.4 manages to generate 32x32->64 mult
instructions for the 32bit mul_u64_u32_shr() code, any GCC after that
fails horribly.

Fix this by providing an explicit mul_u32_u32() function which can be
architcture provided.

Reported-by: Chris Metcalf <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Chris Metcalf <[email protected]> [for tile]
Cc: Christopher S. Hall <[email protected]>
Cc: David Gibson <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Laurent Vivier <[email protected]>
Cc: Liav Rehana <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Parit Bhargava <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>