crypto: caam - Reintroduce DESC_MAX_USED_BYTES

I incorrectly removed DESC_MAX_USED_BYTES when enlarging the size
of the shared descriptor buffers, thus making it four times larger
than what is necessary.  This patch restores the division by four
calculation.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/caam/caamalg.c

@@ -100,7 +100,8 @@
 #define DESC_ABLKCIPHER_DEC_LEN		(DESC_ABLKCIPHER_BASE + \
 					 15 * CAAM_CMD_SZ)
 
-#define DESC_MAX_USED_LEN		(CAAM_DESC_BYTES_MAX - DESC_JOB_IO_LEN)
+#define DESC_MAX_USED_BYTES		(CAAM_DESC_BYTES_MAX - DESC_JOB_IO_LEN)
+#define DESC_MAX_USED_LEN		(DESC_MAX_USED_BYTES / CAAM_CMD_SZ)
 
 #ifdef DEBUG
 /* for print_hex_dumps with line references */