proc/system: fix read always returning 0 #304

Job	Run time
Doxygen	16s
test	33s
Build (nasm, gcc, g++, ubuntu-latest)	20s
Build (gcc-12 g++-12 nasm, gcc-12, g++-12, ubuntu-22.04)	22s
Build (gcc-11 g++-11 nasm, gcc-11, g++-11, ubuntu-22.04)	31s
Build (gcc-10 g++-10 nasm, gcc-10, g++-10, ubuntu-22.04)	20s
Build (gcc-9 g++-9 nasm, gcc-9, g++-9, ubuntu-22.04)	18s
Build (gcc-8 g++-8 nasm, gcc-8, g++-8, ubuntu-20.04)	26s
Build (gcc-7 g++-7 nasm, gcc-7, g++-7, ubuntu-20.04)	27s
Build (nasm, clang, clang++, ubuntu-latest)	18s
Build (clang-14 nasm, clang-14, clang++-14, ubuntu-22.04)	21s
Build (clang-13 nasm, clang-13, clang++-13, ubuntu-22.04)	21s
Build (clang-12 nasm, clang-12, clang++-12, ubuntu-22.04)	23s
Build (clang-11 nasm, clang-11, clang++-11, ubuntu-22.04)	21s
Build (clang-10 nasm, clang-10, clang++-10, ubuntu-20.04)	34s
Build (clang-9 nasm, clang-9, clang++-9, ubuntu-20.04)	48s
Build (clang-8 nasm, clang-8, clang++-8, ubuntu-20.04)	27s
Build (clang-7 nasm, clang-7, clang++-7, ubuntu-20.04)	32s
	7m 38s

Provide feedback