systemcmds:Use CONFIG_BOARD_ROOT_PATH instead of string constant

src/systemcmds/hardfault_log/hardfault_log.c

@@ -1289,7 +1289,7 @@ static void print_usage(void)
 			       "Hardfault type: 0=divide by 0, 1=Assertion, 2=jump to 0x0, 3=write to 0x0 (default=0)", true);
 
 	PRINT_MODULE_USAGE_COMMAND_DESCR("commit",
-					 "Write uncommitted hardfault to /fs/microsd/fault_%i.txt (and rearm, but don't reset)");
+					 "Write uncommitted hardfault to " CONFIG_BOARD_ROOT_PATH "/fault_%i.txt (and rearm, but don't reset)");
 	PRINT_MODULE_USAGE_COMMAND_DESCR("count",
 					 "Read the reboot counter, counts the number of reboots of an uncommitted hardfault (returned as the exit code of the program)");
 	PRINT_MODULE_USAGE_COMMAND_DESCR("reset", "Reset the reboot counter");

src/systemcmds/netman/netman.cpp

@@ -51,7 +51,7 @@
 #include <arpa/inet.h>
 #include <px4_platform_common/shutdown.h>
 
-constexpr char DEFAULT_NETMAN_CONFIG[] = "/fs/microsd/net.cfg";
+constexpr char DEFAULT_NETMAN_CONFIG[] = CONFIG_BOARD_ROOT_PATH "/net.cfg";
 #if defined(CONFIG_NETINIT_DHCPC)
 #  define DEFAULT_PROTO   IPv4PROTO_FALLBACK
 #  define DEFAULT_IP      CONFIG_NETMAN_FALLBACK_IPADDR

src/systemcmds/tests/test_mount.cpp

@@ -62,7 +62,7 @@ int test_mount(int argc, char *argv[])
 	const unsigned iterations = 2000;
 	const unsigned alignments = 10;
 
-	const char *cmd_filename = "/fs/microsd/mount_test_cmds.txt";
+	const char *cmd_filename = CONFIG_BOARD_ROOT_PATH "/mount_test_cmds.txt";
 
 
 	/* check if microSD card is mounted */