Command used for the job:
egrep -rl ' $' --include *.c --include *.h --include  *.s --include  *.inc --include  *.txt *  | xargs sed -i 's/\s\+$//g'

Credits to Grant Murphy from Stack Overflow.

Information: Our current audio macros preclude the definition of root
key and pan (applicable when used in drumsets, aka "keysplit_all") for
GB channels. However, this functionality does exist in m4a--Pokemon
Emerald just happens not to use it. However, for the sake of people
working with custom music, I believe these values should be modifiable
by users.

Additionally, given the recent events that have occurred with this repo,
I would like to make something fully clear: I have indeed looked at the
GBA SDK before, which contains notes on how these sounds are defined;
therefore, I cannot blame you if you reject this PR on the grounds that
the information is "tainted." However, this information is readily
available and matches the same macros used for directsound--it's hardly
information that one would need the source to know.