platform: Use one unified per-HART stack size macro for all platforms

As of today all platforms use 8KB of per-HART stack hence there is
no need for each platform to define its own macro or use the magic
number. Create one macro for all platforms. Platform still can use
its own version if needed.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>

platform/spike/platform.c

@@ -11,7 +11,6 @@
 /* clang-format off */
 
 #define SPIKE_HART_COUNT			8
-#define SPIKE_HART_STACK_SIZE			8192
 
 #define SPIKE_CLINT_ADDR			0x2000000
 
@@ -109,6 +108,6 @@ const struct sbi_platform platform = {
 	.name			= "Spike",
 	.features		= SBI_PLATFORM_DEFAULT_FEATURES,
 	.hart_count		= SPIKE_HART_COUNT,
-	.hart_stack_size	= SPIKE_HART_STACK_SIZE,
+	.hart_stack_size	= SBI_PLATFORM_DEFAULT_HART_STACK_SIZE,
 	.platform_ops_addr	= (unsigned long)&platform_ops
 };