The author intended to split:
1. Former "I" extensions
2. Other "I"-related extensions
but incorrectly separated between "Zihpm" (a supplement of "Zicntr" which is
a former "I" extension) and "Zifencei" (a former "I" extension) while the
author intended making a separation between "Zifencei" and "Zihintpause"
(not a part of "I").
This commit fixes the separation.