[Crypto]: Fix salsa20_8(B) when compiled with -Os optimisation level (

#3491)

trezor-crypto/crypto/scrypt.c

@@ -42,23 +42,20 @@
 #include <stdlib.h>
 #include <string.h>
 
-static void blkcpy(void *, void *, size_t);
+static void blkcpy(uint32_t *, const uint32_t *, size_t);
 static void blkxor(void *, void *, size_t);
 static void salsa20_8(uint32_t[16]);
 static void blockmix_salsa8(uint32_t *, uint32_t *, uint32_t *, size_t);
 static uint64_t integerify(void *, size_t);
 static void smix(uint8_t *, size_t, uint64_t, uint32_t *, uint32_t *);
 
 static void
-blkcpy(void * dest, void * src, size_t len)
+blkcpy(uint32_t * dest, const uint32_t * src, size_t len)
 {
- size_t * D = dest;
- size_t * S = src;
- size_t L = len / sizeof(size_t);
- size_t i;
+ size_t L = len / sizeof(uint32_t);
 
- for (i = 0; i < L; i++)
- D[i] = S[i];
+ for (size_t i = 0; i < L; i++)
+ dest[i] = src[i];
 }
 
 static void