mtd: rawnand: placate "$VARIABLE is used uninitialized" warnings

The compiler is not smart enough to notice that it's impossible for
them to be actually used uninitialized.  Which exact variables trip
here varies depending on random surrounding code; none triggered in
6.1-rc1 but 6.1-rc2 fails on three of these five, despite variables
declared in the very same line having identical flow.

Signed-off-by: Adam Borowski <kilobyte@angband.pl>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20221024092026.42123-1-kilobyte@angband.pl

drivers/mtd/nand/raw/nand_base.c

@@ -5834,7 +5834,7 @@ nand_match_ecc_req(struct nand_chip *chip,
 	int req_step = requirements->step_size;
 	int req_strength = requirements->strength;
 	int req_corr, step_size, strength, nsteps, ecc_bytes, ecc_bytes_total;
-	int best_step, best_strength, best_ecc_bytes;
+	int best_step = 0, best_strength = 0, best_ecc_bytes = 0;
 	int best_ecc_bytes_total = INT_MAX;
 	int i, j;
 
@@ -5915,7 +5915,7 @@ nand_maximize_ecc(struct nand_chip *chip,
 	int step_size, strength, nsteps, ecc_bytes, corr;
 	int best_corr = 0;
 	int best_step = 0;
-	int best_strength, best_ecc_bytes;
+	int best_strength = 0, best_ecc_bytes = 0;
 	int i, j;
 
 	for (i = 0; i < caps->nstepinfos; i++) {