Revert "parisc: Drop LDCW barrier in CAS code when running UP"

This reverts commit e6eb5fe.
We need to optimize it differently. A follow up patch will correct it.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v5.2+

Author: hdeller

arch/parisc/kernel/syscall.S

@@ -641,8 +641,7 @@ cas_action:
 2:	stw	%r24, 0(%r26)
 	/* Free lock */
 #ifdef CONFIG_SMP
-98:	LDCW	0(%sr2,%r20), %r1			/* Barrier */
-99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
 #endif
 	stw	%r20, 0(%sr2,%r20)
 #if ENABLE_LWS_DEBUG
@@ -659,8 +658,7 @@ cas_action:
 	/* Error occurred on load or store */
 	/* Free lock */
 #ifdef CONFIG_SMP
-98:	LDCW	0(%sr2,%r20), %r1			/* Barrier */
-99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
 #endif
 	stw	%r20, 0(%sr2,%r20)
 #if ENABLE_LWS_DEBUG
@@ -864,8 +862,7 @@ cas2_action:
 cas2_end:
 	/* Free lock */
 #ifdef CONFIG_SMP
-98:	LDCW	0(%sr2,%r20), %r1			/* Barrier */
-99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
 #endif
 	stw	%r20, 0(%sr2,%r20)
 	/* Enable interrupts */
@@ -878,8 +875,7 @@ cas2_end:
 	/* Error occurred on load or store */
 	/* Free lock */
 #ifdef CONFIG_SMP
-98:	LDCW	0(%sr2,%r20), %r1			/* Barrier */
-99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
 #endif
 	stw	%r20, 0(%sr2,%r20)
 	ssm	PSW_SM_I, %r0