[posix] update the default channel masks in the configuration file (#9443)

The default supported channel mask is set to 0x7fff000 in the default
configuration file. The dbus client test case sets the channel to 11
which is not valid in the supported channel mask. It causes the CI test
failures in https://github.com/openthread/ot-br-posix/pull/2027.

This commit updates the default supported and preferred channel masks
in the configuration file to avoid the CI test failures.

src/posix/platform/openthread.conf.example

@@ -23,13 +23,12 @@ calibrated_power=11,25,1000,223344
 calibrated_power=26,26,1500,334455
 calibrated_power=26,26,700,445566
 
-
 # The radio supported channel mask that the device is allowed to be on.
 # supported_channel_mask=<RegulatoryDomain>,<ChannelMask>
-supported_channel_mask=ETSI,0x7fff800
-supported_channel_mask=FCC,0x7fff000
+supported_channel_mask=ETSI,0x3fff800
+supported_channel_mask=FCC,0x7fff800
 
 # The radio preferred channel mask that the device prefers to form on.
 # preferred_channel_mask=<RegulatoryDomain>,<ChannelMask>
-preferred_channel_mask=ETSI,0x7fff000
-preferred_channel_mask=FCC,0x7ff7000
+preferred_channel_mask=ETSI,0x1fff800
+preferred_channel_mask=FCC,0x3fff800

tests/scripts/expect/posix-channel-mask.exp

@@ -43,22 +43,22 @@ send "region US\n"
 expect_line "Done"
 
 send "channel supported\n"
-expect "0x7fff000"
+expect "0x7fff800"
 expect_line "Done"
 
 send "channel preferred\n"
-expect "0x7ff7000"
+expect "0x3fff800"
 expect_line "Done"
 
 send "region WW\n"
 expect_line "Done"
 
 send "channel supported\n"
-expect "0x7fff800"
+expect "0x3fff800"
 expect_line "Done"
 
 send "channel preferred\n"
-expect "0x7fff000"
+expect "0x1fff800"
 expect_line "Done"
 
 dispose_node 1