s32 -> int by @benpicco

https://github.com/benpicco/linux_exfat-staging/commit/2ffb5759a305652df17481d750454620f8c32bc6
Don't always show debug messages

CONFIG_EXFAT_DEBUG_MSG is always defined (either by Kconfig if on, or
exfat_config.h since 89d7aab6) so currently debugging messages are
always on.