efi_loader: illegal free in EFI_LOAD_FILE2_PROTOCOL

strsep() changes the address that its first argument points to.
We cannot use the changed address as argument of free().

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>