rpi-eeprom-update: Don't remove update files if run with no arguments

Running 'sudo rpi-eeprom-update' will remove update files from the
boot partition. Since the user may run this command to check if
an update is required it will have the surprising side effect of
removing the pending update applied by the systemd service which
runs 'rpi-eeprom-update -a' at startup.

Move the cleanup code so that it only runs if a manual or automatic
update was requested.

Add an explicit option (-r) to just remove the previous update files.

rpi-eeprom-update

@@ -285,6 +285,7 @@ rpi-eeprom-update [options]... [FILE]
    -h Display help text and exit
    -j Write status information using JSON notation
    -m Write status information to the given file when run without -a or -f
+   -r Removes temporary EEPROM update files from the boot partition.
    -u Install the specified VL805 (USB EEPROM) image file.
 
    To extract the configuration file from an EEPROM image: 
@@ -394,6 +395,7 @@ lookupVersionInfo()
 checkAndApply()
 {
    lookupVersionInfo
+   removePreviousUpdates
 
    # Restrict the automatic updates to the EEPROM types selected by the -A option.
    if [ "${AUTO_UPDATE_VL805}" != 1 ]; then
@@ -417,6 +419,7 @@ checkAndApply()
 
 fileUpdate()
 {
+   removePreviousUpdates
    echo "*** INSTALLING ${BOOTLOADER_UPDATE_IMAGE} ${VL805_UPDATE_IMAGE} ***"
 
    if [ -n "${BOOTLOADER_UPDATE_IMAGE}" ]; then
@@ -501,7 +504,7 @@ AUTO_UPDATE_VL805=0
 MACHINE_OUTPUT=""
 JSON_OUTPUT="no"
 
-while getopts A:adhf:m:ju: option; do
+while getopts A:adhf:m:ju:r option; do
    case "${option}" in
    A)
       if [ "${OPTARG}" = "bootloader" ]; then
@@ -525,6 +528,11 @@ while getopts A:adhf:m:ju: option; do
       ;;
    h) usage
       ;;
+   r) [ "$(id -u)" = "0" ] || die "* Must be run as root - try 'sudo rpi-eeprom-update -r'"
+      echo "Removing temporary files from previous EEPROM update"
+      removePreviousUpdates
+      exit 0
+      ;;
    u) VL805_UPDATE_IMAGE="${OPTARG}"
       ;;
    *) echo "Unknown argument \"${option}\""
@@ -534,7 +542,6 @@ while getopts A:adhf:m:ju: option; do
 done
 
 checkDependencies
-removePreviousUpdates
 if [ "${AUTO_UPDATE_BOOTLOADER}" = 1 ] || [ "${AUTO_UPDATE_VL805}" = 1 ]; then
    if vcgencmd bootloader_config | grep FREEZE_VERSION=1; then
       echo "EEPROM version is frozen. Skipping update"