util: resolve m5op name mismatching in m5op headers.

util: resolve m5op name mismatching in m5op headers.

Two m5op, load_symbol and dist_toggle_sync are defined with
different name in C and asm version headers 'm5ops.h'
The m5ops are named to m5_load_symbol() and m5_dist_toggle_sync().

Change-Id: I9630d74f3fb95bc3dc5fa082778d8f6eaa49b3cb
Reviewed-on: https://gem5-review.googlesource.com/6481
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>