Fix: `void *` arithmetic compiler warning

Fix: `void *` arithmetic compiler warning

Fixes warning "pointer of type ‘void *’ used in subtraction [-Wpointer-arith]"
which was observed on gcc 11.3.0 on Ubuntu 22.04 LTS Linux 6.3.0 RC7 x86-64.

This warning was enabled by the flag `-Wpedantic`.

Link: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wpointer-arith
Signed-off-by: Gerrit Klein <therealthingy95@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Icfcf1d39bcde3730bf38c9ec6ed1521ed4503625