LoongArch: Remove unused setup_profiling_timer() function

setup_profiling_timer() is not used by any code at this point. Since a
default weak implementation exists, there is no need to still keep this
arch-specific definition around. Remove it along with the now-redundant
profile header includes.

Signed-off-by: Anthony Iliopoulos <ailiop@suse.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>