esp.c: don't clear the SCSI phase when reading ESP_RINTR

According to the documentation ESP_RSTAT is cleared (except the STAT_TC bit)
when ESP_RINTR is read. This should not include the SCSI bus phase bits which
are currently live from the SCSI bus, otherwise the current SCSI phase is lost
when clearing an end-of-transfer interrupt.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: Helge Deller <deller@gmx.de>
Tested-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20240112125420.514425-72-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

hw/scsi/esp.c

@@ -1128,7 +1128,7 @@ uint64_t esp_reg_read(ESPState *s, uint32_t saddr)
         val = s->rregs[ESP_RINTR];
         s->rregs[ESP_RINTR] = 0;
         esp_lower_irq(s);
-        s->rregs[ESP_RSTAT] &= ~STAT_TC;
+        s->rregs[ESP_RSTAT] &= STAT_TC | 7;
         /*
          * According to the datasheet ESP_RSEQ should be cleared, but as the
          * emulation currently defers information transfers to the next TI