ARM: dts: dra7xx: Increase spi-max-frequency to 76.8MHz for QSPI

According to AM572x DM SPRS953A, QSPI maximum bus speed can be 76.8MHz.
Therefore, increase the spi-max-frequency value of QSPI node to 76.8MHz
for DRA74 and DRA72 evm. This improves flash raw read speed by ~2MB/s.
Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/dra7-evm.dts

@@ -664,10 +664,10 @@ &cpu0 {
 &qspi {
 	status = "okay";
 
-	spi-max-frequency = <64000000>;
+	spi-max-frequency = <76800000>;
 	m25p80@0 {
 		compatible = "s25fl256s1";
-		spi-max-frequency = <64000000>;
+		spi-max-frequency = <76800000>;
 		reg = <0>;
 		spi-tx-bus-width = <1>;
 		spi-rx-bus-width = <4>;

arch/arm/boot/dts/dra72-evm-common.dtsi

@@ -681,10 +681,10 @@ &dcan1 {
 &qspi {
 	status = "okay";
 
-	spi-max-frequency = <64000000>;
+	spi-max-frequency = <76800000>;
 	m25p80@0 {
 		compatible = "s25fl256s1";
-		spi-max-frequency = <64000000>;
+		spi-max-frequency = <76800000>;
 		reg = <0>;
 		spi-tx-bus-width = <1>;
 		spi-rx-bus-width = <4>;