powerpc/fadump: invoke ibm,os-term with rtas_call_unlocked()

Invoke ibm,os-term call with rtas_call_unlocked(), without using the
RTAS spinlock, to avoid deadlock in the unlikely event of a machine
crash while making an RTAS call.
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230609071404.425529-1-hbathini@linux.ibm.com

arch/powerpc/kernel/rtas.c

@@ -1587,6 +1587,7 @@ static bool ibm_extended_os_term;
 void rtas_os_term(char *str)
 {
 	s32 token = rtas_function_token(RTAS_FN_IBM_OS_TERM);
+	static struct rtas_args args;
 	int status;
 
 	/*
@@ -1607,7 +1608,8 @@ void rtas_os_term(char *str)
 	 * schedules.
 	 */
 	do {
-		status = rtas_call(token, 1, 1, NULL, __pa(rtas_os_term_buf));
+		rtas_call_unlocked(&args, token, 1, 1, NULL, __pa(rtas_os_term_buf));
+		status = be32_to_cpu(args.rets[0]);
 	} while (rtas_busy_delay_time(status));
 
 	if (status != 0)