arm64: dts: ti: k3-am65-main: reduce memory reserved for msmc_sram1

msmc_sram1 sub-node in msmc_ram DT node is used for Watchdog
sample implementation. Currently it reseves 0xd0000 of MSMC
SRAM for Watchdog function though it needs only about 64K
(0x10000). This leaves no memory available for general use
by drivers in Linux kernel. This causes icssg_prueth driver
to fail probe because of msmc memory allocation failure.
So reduce the size of msmc_sram1 to 0x10000.  While fixing
this, also add a cautionary note to alert user from blindly
reserving memory in msmc_ram DT node of DTS.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>

arch/arm64/boot/dts/ti/k3-am65-main.dtsi

@@ -14,12 +14,20 @@
 		#size-cells = <1>;
 		ranges = <0x0 0x0 0x70000000 0x200000>;
 
+		/* WARNING!!! No All non-reserved memory
+		 * is available for use. For example
+		 * ICSSG PRUETH needs 98K * 3 = 294K.
+		 * So reserve memory below carefully
+		 * after reviewing current usage. One
+		 * way is to check the instances of
+		 * dts nodes pointing to msmc_ram
+		 */
 		atf-sram@0 {
 			reg = <0x0 0x20000>;
 		};
 
 		msmc_sram1: msmc-sram1@20000 {
-			reg = <0x20000 0xd0000>;
+			reg = <0x20000 0x10000>;
 		};
 
 		sysfw-sram@f0000 {