[posix] add argument to set max power table (#4878)

This commit adds a max power table for POSIX platform, which can
customize the max allowed transmit power of each channel with the
command line argument --max-power-table.

tests/scripts/expect/posix-max-power-table.exp

@@ -0,0 +1,56 @@
+#!/usr/bin/expect -f
+#
+#  Copyright (c) 2020, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+#
+
+# allows 11-25 and forbidden 26
+spawn $env(OT_COMMAND) --max-power-table 11,12,13,14,15,16,17,18,19,20,21,22,23,24,-1,0x7f $env(RCP_COMMAND) 1
+set timeout 1
+expect_after {
+    timeout { exit 1 }
+}
+send "channel supported\n"
+expect "0x3fff800"
+expect "Done"
+send "channel preferred\n"
+expect "0x3fff800"
+expect "Done"
+send "\x04"
+expect eof
+# allows all channels by default
+spawn $env(OT_COMMAND) $env(RCP_COMMAND) 1
+set timeout 1
+expect_after {
+    timeout { exit 1 }
+}
+send "channel supported\n"
+expect "0x7fff800"
+expect "Done"
+send "channel preferred\n"
+expect "0x7fff800"
+expect "Done"
+send_user "\r\n"