math: Remove powerpc e_hypot

math: Remove powerpc e_hypot

The generic implementation is shows only slight worse performance:

POWER10    reciprocal-throughput    latency
master                   8.28478    13.7253
new hypot                7.21945    13.1933

POWER9     reciprocal-throughput    latency
master                   13.4024    14.0967
new hypot                14.8479    15.8061

POWER8     reciprocal-throughput    latency
master                   15.5767    16.8885
new hypot                16.5371    18.4057

One way to improve might to make gcc generate xsmaxdp/xsmindp for
fmax/fmin (it onl does for -ffast-math, clang does for default
options).

Checked on powerpc64-linux-gnu (power8) and powerpc64le-linux-gnu
(power9).