riscv: Remove SHADOW_OVERFLOW_STACK_SIZE macro

The commit be97d0d ("riscv: VMAP_STACK overflow
detection thread-safe") got rid of `shadow_stack`,
so SHADOW_OVERFLOW_STACK_SIZE should be removed too.

Fixes: be97d0d ("riscv: VMAP_STACK overflow detection thread-safe")
Signed-off-by: Song Shuai <songshuaishuai@tinylab.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20231211110331.359534-1-songshuaishuai@tinylab.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Song Shuai

arch/riscv/include/asm/thread_info.h

@@ -28,7 +28,6 @@
 
 #define THREAD_SHIFT            (PAGE_SHIFT + THREAD_SIZE_ORDER)
 #define OVERFLOW_STACK_SIZE     SZ_4K
-#define SHADOW_OVERFLOW_STACK_SIZE (1024)
 
 #define IRQ_STACK_SIZE		THREAD_SIZE