Btrfs: remove some no-op casts

We cast 0 to a u8 but then because of type promotion, it's immediately
cast to int back to int before we do a bitwise negate.  The cast doesn't
matter in this case, the code works as intended.  It causes a static
checker warning though so let's remove it.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -5569,7 +5569,7 @@ void le_bitmap_set(u8 *map, unsigned int start, int len)
 		*p |= mask_to_set;
 		len -= bits_to_set;
 		bits_to_set = BITS_PER_BYTE;
-		mask_to_set = ~(u8)0;
+		mask_to_set = ~0;
 		p++;
 	}
 	if (len) {
@@ -5589,7 +5589,7 @@ void le_bitmap_clear(u8 *map, unsigned int start, int len)
 		*p &= ~mask_to_clear;
 		len -= bits_to_clear;
 		bits_to_clear = BITS_PER_BYTE;
-		mask_to_clear = ~(u8)0;
+		mask_to_clear = ~0;
 		p++;
 	}
 	if (len) {
@@ -5679,7 +5679,7 @@ void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
 		kaddr[offset] |= mask_to_set;
 		len -= bits_to_set;
 		bits_to_set = BITS_PER_BYTE;
-		mask_to_set = ~(u8)0;
+		mask_to_set = ~0;
 		if (++offset >= PAGE_SIZE && len > 0) {
 			offset = 0;
 			page = eb->pages[++i];
@@ -5721,7 +5721,7 @@ void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
 		kaddr[offset] &= ~mask_to_clear;
 		len -= bits_to_clear;
 		bits_to_clear = BITS_PER_BYTE;
-		mask_to_clear = ~(u8)0;
+		mask_to_clear = ~0;
 		if (++offset >= PAGE_SIZE && len > 0) {
 			offset = 0;
 			page = eb->pages[++i];