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/ls1021a.dtsi b/arch/arm/dts/ls1021a.dtsi
index e419d9c..0eeec43 100644
--- a/arch/arm/dts/ls1021a.dtsi
+++ b/arch/arm/dts/ls1021a.dtsi
@@ -169,14 +169,12 @@
 		};
 
 		qspi: quadspi@1550000 {
-			compatible = "fsl,vf610-qspi";
+			compatible = "fsl,ls1021a-qspi";
 			#address-cells = <1>;
 			#size-cells = <0>;
 			reg = <0x1550000 0x10000>,
-				<0x40000000 0x4000000>;
+				<0x40000000 0x1000000>;
 			reg-names = "QuadSPI", "QuadSPI-memory";
-			num-cs = <2>;
-			big-endian;
 			status = "disabled";
 		};