crypto - Avoid free() namespace collision

gcc-10 complains about using the name of a standard library
function in the kernel, as we are not building with -ffreestanding:

crypto/xts.c:325:13: error: conflicting types for built-in function 'free'; expected 'void(void *)' [-Werror=builtin-declaration-mismatch]
  325 | static void free(struct skcipher_instance *inst)
      |             ^~~~
crypto/lrw.c:290:13: error: conflicting types for built-in function 'free'; expected 'void(void *)' [-Werror=builtin-declaration-mismatch]
  290 | static void free(struct skcipher_instance *inst)
      |             ^~~~
crypto/lrw.c:27:1: note: 'free' is declared in header '<stdlib.h>'

The xts and lrw cipher implementations run into this because they do
not use the conventional namespaced function names.

It might be better to rename all local functions in those files to
help with things like 'ctags' and 'grep', but just renaming these two
avoids the build issue. I picked the more verbose crypto_xts_free()
and crypto_lrw_free() names for consistency with several other drivers
that do use namespaced function names.

Fixes: f1c131b4 ("crypto: xts - Convert to skcipher")
Fixes: 700cb3f5 ("crypto: lrw - Convert to skcipher")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>