perf hist: Shrink struct hist_entry size

perf hist: Shrink struct hist_entry size

Reorder the struct fields by size to reduce paddings and reduce
struct simd_flags size from 8 to 1 byte.

This reduces struct hist_entry size by 8 bytes (592->584),
and leaves a single more usable 6 byte padding hole.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Link: https://lore.kernel.org/r/7c1cb1c8f9901e945162701ba7269d0f9c70be89.1739437531.git.dvyukov@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>