timer: use 64-bit specific code on more platforms
timer: use 64-bit specific code on more platforms

64bit load and store will be an atomic operation on all the
64bit processors.
Change RTE_ARCH_X86_64 to RTE_ARCH_64 to reflect the case.

Fixes: 9b15ba895b9f ("timer: use a skip list")
Cc: stable@dpdk.org

Signed-off-by: Jerin Jacob <5bca7d2a432bc0f5422b70b2701a4e4fa32edd00@caviumnetworks.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk