net: encx24j600: Fix invalid logic in reading of MISTAT register

A loop for reading MISTAT register continues while regmap_read() fails
and (mistat & BUSY), but if regmap_read() fails a value of mistat is
undefined.

The patch proposes to check for BUSY flag only when regmap_read()
succeed. Compile test only.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: d70e5326 ("net: Microchip encx24j600 driver")
Signed-off-by: Valentina Goncharenko <goncharenko.vp@ispras.ru>
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/encx24j600-regmap.c

@@ -359,7 +359,7 @@ static int regmap_encx24j600_phy_reg_read(void *context, unsigned int reg,
 		goto err_out;
 
 	usleep_range(26, 100);
-	while (((ret = regmap_read(ctx->regmap, MISTAT, &mistat)) != 0) &&
+	while (((ret = regmap_read(ctx->regmap, MISTAT, &mistat)) == 0) &&
 	       (mistat & BUSY))
 		cpu_relax();
 
@@ -397,7 +397,7 @@ static int regmap_encx24j600_phy_reg_write(void *context, unsigned int reg,
 		goto err_out;
 
 	usleep_range(26, 100);
-	while (((ret = regmap_read(ctx->regmap, MISTAT, &mistat)) != 0) &&
+	while (((ret = regmap_read(ctx->regmap, MISTAT, &mistat)) == 0) &&
 	       (mistat & BUSY))
 		cpu_relax();