firmware: Improve parsing of manifest.json from recovery USB

Fixes extraction of firmware for nissa-based boards.

Signed-off-by: Matt DeVillier <[email protected]>

Author: MrChromebox

firmware.sh

@@ -791,7 +791,7 @@ function extract_firmware_from_recovery_usb()
         fi
     elif [ -f "$_unpacked/manifest.json" ]; then
         _version=$(grep -m1 -A4 "$_board\":" "$_unpacked/manifest.json" | grep -m1 "rw" | sed 's/.*\(rw.*\)/\1/' | sed 's/.*\("Google.*\)/\1/' | cut -f2 -d'"')
-        _bios_image=$(grep -m1 -A7 "$_board\":" "$_unpacked/manifest.json" | grep -m1 "image" | sed 's/.*"image": //' | cut -f2 -d'"')
+        _bios_image=$(grep -m1 -A10 "$_board\":" "$_unpacked/manifest.json" | grep -m1 "image" | sed 's/.*"image": //' | cut -f2 -d'"')
     else
         if [ -f $_unpacked/VERSION ]; then
             _version=$(cat $_unpacked/VERSION | grep BIOS\ version: | cut -f2 -d: | tr -d \ )