lightnvm: pblk: improve naming for internal req.

Each request type sent to the LightNVM subsystem requires different
metadata. Until now, we have tailored this metadata based on write, read
and erase commands. However, pblk uses different metadata for internal
writes that do not hit the write buffer. Instead of abusing the metadata
for reads, create a new request type - internal write to improve
code readability.

In the process, create internal values for each I/O type instead of
abusing the READ/WRITE macros, as suggested by Christoph.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk.h

@@ -55,11 +55,16 @@
 		for ((i) = 0, rlun = &(pblk)->luns[0]; \
 			(i) < (pblk)->nr_luns; (i)++, rlun = &(pblk)->luns[(i)])
 
-#define ERASE 2 /* READ = 0, WRITE = 1 */
-
 /* Static pool sizes */
 #define PBLK_GEN_WS_POOL_SIZE (2)
 
+enum {
+	PBLK_READ		= READ,
+	PBLK_WRITE		= WRITE,/* Write from write buffer */
+	PBLK_WRITE_INT,			/* Internal write - no write buffer */
+	PBLK_ERASE,
+};
+
 enum {
 	/* IO Types */
 	PBLK_IOTYPE_USER	= 1 << 0,
@@ -1132,7 +1137,7 @@ static inline int pblk_set_progr_mode(struct pblk *pblk, int type)
 
 	flags = geo->plane_mode >> 1;
 
-	if (type == WRITE)
+	if (type == PBLK_WRITE)
 		flags |= NVM_IO_SCRAMBLE_ENABLE;
 
 	return flags;