[PATCH] LoongArch: signal.c: add header file to fix build error

[Randy Dunlap]

loongarch's signal.c uses rseq_signal_deliver() so it should
pull in the appropriate header to prevent a build error:

../arch/loongarch/kernel/signal.c: In function 'handle_signal':
../arch/loongarch/kernel/signal.c:1034:9: error: implicit declaration of function 'rseq_signal_deliver' [-Werror=implicit-function-declaration]
 1034 |         rseq_signal_deliver(ksig, regs);
      |         ^~~~~~~~~~~~~~~~~~~

Fixes: b74baf4ad05b ("LoongArch: Add signal handling support")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
M:	Huacai Chen <chenhuacai@xxxxxxxxxx>
R:	WANG Xuerui <kernel@xxxxxxxxxx>
L:	loongarch@xxxxxxxxxxxxxxx

---
 arch/loongarch/kernel/signal.c |    1 +
 1 file changed, 1 insertion(+)

diff -- a/arch/loongarch/kernel/signal.c b/arch/loongarch/kernel/signal.c
--- a/arch/loongarch/kernel/signal.c
+++ b/arch/loongarch/kernel/signal.c
@@ -15,6 +15,7 @@
 #include <linux/context_tracking.h>
 #include <linux/entry-common.h>
 #include <linux/irqflags.h>
+#include <linux/rseq.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/personality.h>