s390x/css: fix PMCW invalid mask

Previously, we required bits 5, 6 and 7 to be zero (0x07 == 0b111). But,
as per the principles of operation, bit 5 is ignored in MSCH and bits 0,
1, 6 and 7 need to be zero.

As both PMCW_FLAGS_MASK_INVALID and ioinst_schib_valid() are only used
by ioinst_handle_msch(), adjust the mask accordingly.

Fixes: db1c8f53bfb1 ("s390: Channel I/O basic definitions.")
Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20211216131657.1057978-1-nrb@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

include/hw/s390x/ioinst.h

@@ -107,7 +107,7 @@ QEMU_BUILD_BUG_MSG(sizeof(PMCW) != 28, "size of PMCW is wrong");
 #define PMCW_FLAGS_MASK_MP 0x0004
 #define PMCW_FLAGS_MASK_TF 0x0002
 #define PMCW_FLAGS_MASK_DNV 0x0001
-#define PMCW_FLAGS_MASK_INVALID 0x0700
+#define PMCW_FLAGS_MASK_INVALID 0xc300
 
 #define PMCW_CHARS_MASK_ST 0x00e00000
 #define PMCW_CHARS_MASK_MBFC 0x00000004