linux: enable firmware loading from /storage/.config/firmware/

from Documentation/firmware_class/README:

 ....
 1), kernel(driver):
        - calls request_firmware(&fw_entry, $FIRMWARE, device)
        - kernel searchs the fimware image with name $FIRMWARE directly
        in the below search path of root filesystem:
                User customized search path by module parameter 'path'[1]
                "/lib/firmware/updates/" UTS_RELEASE,
                "/lib/firmware/updates",
                "/lib/firmware/" UTS_RELEASE,
                "/lib/firmware"
        - If found, goto 7), else goto 2)

        [1], the 'path' is a string parameter which length should be less
        than 256, user should pass 'firmware_class.path=$CUSTOMIZED_PATH'
        if firmware_class is built in kernel(the general situation)
  ....

can also be done via boot parameter but I preder symlinking
pkgconf: update to pkgconf-0.9.7