PAPR v2.12 defines a new hypercall, H_WATCHDOG.  The hypercall permits
guest control of one or more virtual watchdog timers.
Add the opcode for the H_WATCHDOG hypercall to hvcall.h.  While here,
add a definition for H_NOOP, a possible return code for H_WATCHDOG.
Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220713202335.1217647-2-cheloha@linux.ibm.com
 #define H_P7           -60
 #define H_P8           -61
 #define H_P9           -62
+#define H_NOOP         -63
 #define H_TOO_BIG      -64
 #define H_UNSUPPORTED  -67
 #define H_OVERLAP      -68
 #define H_RPT_INVALIDATE       0x448
 #define H_SCM_FLUSH            0x44C
 #define H_GET_ENERGY_SCALE_INFO        0x450
-#define MAX_HCALL_OPCODE       H_GET_ENERGY_SCALE_INFO
+#define H_WATCHDOG             0x45C
+#define MAX_HCALL_OPCODE       H_WATCHDOG
 
 /* Scope args for H_SCM_UNBIND_ALL */
 #define H_UNBIND_SCOPE_ALL (0x1)