firmware-utiles: add *.attr for GPIO symbolic links

firmware-utiles: add *.attr for GPIO symbolic links

To recognize the polarity of each GPIO, we need to expose the information from
chromeos_acpi interface.

BUG=chrome-os-partner:1940
TEST=(on mario, BIOS ver = G5) gpio_setup; cd /home/gpio; ls -l
 # complete output: (output_header[1-7] is stripped)
 # debug_header_0 -> /sys/class/gpio/gpio201/value
 # debug_header_0.attr -> /sys/bus/platform/devices/chromeos_acpi/GPIO.3/GPIO.1
 # developer_switch -> /sys/class/gpio/gpio193/value
 # developer_switch.attr -> /sys/bus/platform/devices/chromeos_acpi/GPIO.1/GPIO.1
 # recovery_button -> /sys/class/gpio/gpio230/value
 # recovery_button.attr -> /sys/bus/platform/devices/chromeos_acpi/GPIO.0/GPIO.1
 # write_protect -> /sys/class/gpio/gpio226/value
 # write_protect.attr -> /sys/bus/platform/devices/chromeos_acpi/GPIO.2/GPIO.1
 for X in *.attr; do echo $X - $(cat $X); done
 # debug_header_0.attr - 0
 # developer_switch.attr - 1
 # recovery_button.attr - 0
 # write_protect.attr - 0 (this should be 1 in new BIOS)

Change-Id: Ib42b4662c4369112a8f4fb69989d62f2d1b76590

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=beb9877

[Hung-Te, 2011-01-19 03:00:18]

Any updates? We will need this in order to allow Alex factory tests to work.

[Randall Spangler, 2011-01-20 00:52:55]

LGTM, thanks