target/xtensa: Include missing 'qemu/atomic.h' header

Since commit fa92bd4af7 ("target/xtensa: fix access to
the INTERRUPT SR") these files use QEMU atomic API.
Explicit the header inclusion instead of relying on
implicit and indirect inclusion.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230828221314.18435-10-philmd@linaro.org>

hw/xtensa/pic_cpu.c

@@ -30,6 +30,7 @@
 #include "hw/irq.h"
 #include "qemu/log.h"
 #include "qemu/timer.h"
+#include "qemu/atomic.h"
 
 void check_interrupts(CPUXtensaState *env)
 {

target/xtensa/exc_helper.c

@@ -31,6 +31,7 @@
 #include "cpu.h"
 #include "exec/helper-proto.h"
 #include "qemu/host-utils.h"
+#include "qemu/atomic.h"
 #include "exec/exec-all.h"
 
 void HELPER(exception)(CPUXtensaState *env, uint32_t excp)

target/xtensa/op_helper.c

@@ -30,6 +30,7 @@
 #include "exec/helper-proto.h"
 #include "qemu/host-utils.h"
 #include "exec/exec-all.h"
+#include "qemu/atomic.h"
 #include "qemu/timer.h"
 
 #ifndef CONFIG_USER_ONLY