ubsan: add prototypes for internal functions

Most of the functions in ubsan that are only called from generated
code don't have a prototype, which W=1 builds warn about:

lib/ubsan.c:226:6: error: no previous prototype for '__ubsan_handle_divrem_overflow' [-Werror=missing-prototypes]
lib/ubsan.c:307:6: error: no previous prototype for '__ubsan_handle_type_mismatch' [-Werror=missing-prototypes]
lib/ubsan.c:321:6: error: no previous prototype for '__ubsan_handle_type_mismatch_v1' [-Werror=missing-prototypes]
lib/ubsan.c:335:6: error: no previous prototype for '__ubsan_handle_out_of_bounds' [-Werror=missing-prototypes]
lib/ubsan.c:352:6: error: no previous prototype for '__ubsan_handle_shift_out_of_bounds' [-Werror=missing-prototypes]
lib/ubsan.c:394:6: error: no previous prototype for '__ubsan_handle_builtin_unreachable' [-Werror=missing-prototypes]
lib/ubsan.c:404:6: error: no previous prototype for '__ubsan_handle_load_invalid_value' [-Werror=missing-prototypes]

Add prototypes for all of these to lib/ubsan.h, and remove the
one that was already present in ubsan.c.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Fangrui Song <maskray@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230517125102.930491-1-arnd@kernel.org