lib/ubsan.c: fix gcc-10 warnings

The latest compiler expects slightly different function prototypes
for the ubsan helpers:

  lib/ubsan.c:192:6: error: conflicting types for built-in function '__ubsan_handle_add_overflow'; expected 'void(void *, void *, void *)' [-Werror=builtin-declaration-mismatch]
    192 | void __ubsan_handle_add_overflow(struct overflow_data *data,
        |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~
  lib/ubsan.c:200:6: error: conflicting types for built-in function '__ubsan_handle_sub_overflow'; expected 'void(void *, void *, void *)' [-Werror=builtin-declaration-mismatch]
    200 | void __ubsan_handle_sub_overflow(struct overflow_data *data,
        |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~
  lib/ubsan.c:207:6: error: conflicting types for built-in function '__ubsan_handle_mul_overflow'; expected 'void(void *, void *, void *)' [-Werror=builtin-declaration-mismatch]
    207 | void __ubsan_handle_mul_overflow(struct overflow_data *data,
        |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~
  lib/ubsan.c:214:6: error: conflicting types for built-in function '__ubsan_handle_negate_overflow'; expected 'void(void *, void *)' [-Werror=builtin-declaration-mismatch]
    214 | void __ubsan_handle_negate_overflow(struct overflow_data *data,
        |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  lib/ubsan.c:234:6: error: conflicting types for built-in function '__ubsan_handle_divrem_overflow'; expected 'void(void *, void *, void *)' [-Werror=builtin-declaration-mismatch]
    234 | void __ubsan_handle_divrem_overflow(struct overflow_data *data,
        |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Change the Linux implementation to match these, using a local typed
pointer.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Julien Grall <julien.grall@arm.com>
Link: http://lkml.kernel.org/r/20200429185948.4189600-1-arnd@arndb.de


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>