net: sparx5: Fix initialization of variables on stack

The variables 'res' inside the functions sparx5_ptp_get_1ppm and
sparx5_ptp_get_nominal_value was not initialized. So in case of the default
case of the switch after, it would return an uninitialized variable.
This makes also the clang builds to failed.

Fixes: 0933bd0 ("net: sparx5: Add support for ptp clocks")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Link: https://lore.kernel.org/r/20220304140918.3356873-1-horatiu.vultur@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/microchip/sparx5/sparx5_ptp.c

@@ -32,7 +32,7 @@ static u64 sparx5_ptp_get_1ppm(struct sparx5 *sparx5)
 	 * (1/1000000)/((2^-59)/X)
 	 */
 
-	u64 res;
+	u64 res = 0;
 
 	switch (sparx5->coreclock) {
 	case SPX5_CORE_CLOCK_250MHZ:
@@ -54,7 +54,7 @@ static u64 sparx5_ptp_get_1ppm(struct sparx5 *sparx5)
 
 static u64 sparx5_ptp_get_nominal_value(struct sparx5 *sparx5)
 {
-	u64 res;
+	u64 res = 0;
 
 	switch (sparx5->coreclock) {
 	case SPX5_CORE_CLOCK_250MHZ: