cpukit/score/cpu/or1k: Fix the context validation

_CPU_Context_validate() ignored its pattern and filled the registers
with a counter, so the three tasks of spcontext01 wrote the same values
and a leak between them could not be seen.  It kept the entry stack
pointer in r31 and then filled r31 with that counter, so the comparison
of the stack pointer could not hold and the routine returned on its
first pass, which hung the test.  _CPU_Context_volatile_clobber()
covered eight of the volatile registers.

The stack pointer is compared through the frame, since no register is
left for it.

Close #5686.

Assisted-by: Claude:claude-opus-5 claude-code
Signed-off-by: Sebastian Huber <sebastian.huber@embedded-brains.de>

cpukit/score/cpu/or1k/or1k-context-volatile-clobber.S

@@ -33,22 +33,36 @@
 
 .section .text
 
+/*
+ * The volatile registers of the ABI are the arguments r3 to r8, the return
+ * address r9, the return values r11 and r12, and the odd numbered registers
+ * from r13 on.  The thread pointer r10 is not one of them.
+ */
+
+.macro	clobber_register reg, inc
+	l.addi	r\reg, r3, \inc
+.endm
+
 PUBLIC(_CPU_Context_volatile_clobber)
 SYM(_CPU_Context_volatile_clobber):
 
-.macro clobber_register reg
-  l.addi r0, r0, -1
-  l.addi  \reg, r0, 0
-.endm
+	clobber_register	4, 1
+	clobber_register	5, 2
+	clobber_register	6, 3
+	clobber_register	7, 4
+	clobber_register	8, 5
+	clobber_register	11, 6
+	clobber_register	12, 7
+	clobber_register	13, 8
+	clobber_register	15, 9
+	clobber_register	17, 10
+	clobber_register	19, 11
+	clobber_register	21, 12
+	clobber_register	23, 13
+	clobber_register	25, 14
+	clobber_register	27, 15
+	clobber_register	29, 16
+	clobber_register	31, 17
 
-  clobber_register  r3
-  clobber_register  r4
-  clobber_register  r5
-  clobber_register  r6
-  clobber_register  r7
-  clobber_register  r8
-  clobber_register  r13
-  clobber_register  r31
-
-  l.jr  r9
-  l.nop
+	l.jr	r9
+	 l.nop