treewide: Update fsl qspi node dt properties as per spi-mem driver

According to new qspi driver, some properties like "bus-num, num-cs,
big-endian" are no longer used. Device endiannes can be determined from
device-type data in driver.

Now use board specific compatibles, generic node names and specific
labels to align with linux device-tree properties.

Also consolidate spi-max-frequency to 50Mhz treewide.

Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/arch/arm/dts/fsl-ls1012a-rdb.dtsi b/arch/arm/dts/fsl-ls1012a-rdb.dtsi
index 55155fd..3757051 100644
--- a/arch/arm/dts/fsl-ls1012a-rdb.dtsi
+++ b/arch/arm/dts/fsl-ls1012a-rdb.dtsi
@@ -19,14 +19,13 @@
 };
 
 &qspi {
-	bus-num = <0>;
 	status = "okay";
 
-	qflash0: s25fl128s@0 {
+	s25fs512s0: flash@0 {
 		#address-cells = <1>;
 		#size-cells = <1>;
 		compatible = "jedec,spi-nor";
-		spi-max-frequency = <20000000>;
+		spi-max-frequency = <50000000>;
 		reg = <0>;
 	};
 };