gprof: fix odd inst len hist scale calculation

gprof: fix odd inst len hist scale calculation

With even instruction sizes, this rounding never truncated.
Xtensa CPUs mostly use 2-3 byte instructions, and this can lead
to a histogram being captured with an odd length address range.

This small truncation prevented gprof from parsing gmon.out files
containing multiple histograms when at least one of them has an
odd address range length and another has any other address range.

Signed-off-by: Richard Allen <rsaxvc@gmail.com>