firmware-utils: update to git HEAD

firmware-utils: update to git HEAD

 7e6f69b npk_pack_kernel: add tool for creating MikroTik NPK kernel packages
 d3f8b6e zynsig: add new tool for creating images for the ZyXEL GS1920 series
 9fa340d ptgen: create separate images for gpt data structure
 78d8084 ptgen: allow image generation for a specified disk size
 3f2d148 ptgen: allow non-default placement of gpt entry table
 f1f98b0 ptgen: do not create stub partition to fill a gap if gap caused by alignment
 6ea8b6d ptgen: fix protective MBR partition size
 febfef7 ptgen: use long long instead of long for sizes
 996dc48 ptgen: fix misprint and simplify calculation a bit
 0725c3d build: require CMake >= 3.5 due to dropped legacy support

Signed-off-by: Daniel Golle <[email protected]>