xtensa: gdbstub: fix compiler warning about discarding const

Inside copy_to_ctx(), we are typecasting the stack pointer into
a 32-bit array pointer, and there was unbalanced const between
two sides. Since we should not be modifying anything inside
that array, add const to the 32-bit array pointer too. So now
the compiler will not complain about discarding the const
qualifier.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

arch/xtensa/core/gdbstub.c

@@ -427,7 +427,7 @@ static void copy_to_ctx(struct gdb_ctx *ctx, const struct arch_esf *stack)
 	struct xtensa_register *reg;
 	int idx, num_laddr_regs;
 
-	uint32_t *bsa = *(const int **)stack;
+	const uint32_t *bsa = *(const int **)stack;
 
 	if (bsa - (const uint32_t *)stack > 12) {
 		num_laddr_regs = 16;