BRT: Fix ranges to blocks conversion math

BRT_RANGESIZE_TO_NBLOCKS() takes number of ranges as its argument.
To get number of blocks we should multiply it by the entry size,
not divide by it, as it was due to missing parentheses.

Before #17875 this could cause small memory corruptions for vdevs
bigger than 64TB, but the change made the bug more noticeable.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Closes #17886
Closes #17915

Author: amotin

include/sys/brt_impl.h

@@ -65,7 +65,7 @@ _Static_assert(BRT_RANGESIZE / SPA_MINBLOCKSIZE <= UINT16_MAX,
  */
 #define	BRT_BLOCKSIZE	(32 * 1024)
 #define	BRT_RANGESIZE_TO_NBLOCKS(size)					\
-	(((size) - 1) / BRT_BLOCKSIZE / sizeof (uint16_t) + 1)
+	(((size) - 1) / (BRT_BLOCKSIZE / sizeof (uint16_t)) + 1)
 
 #define	BRT_LITTLE_ENDIAN	0
 #define	BRT_BIG_ENDIAN		1