rkflashtool: add infocr() helper function

infocr() is used for printing to stderr using a carriage return character '\r'
Makefile: fix ld warning on OS X

option -s is obsolete and being ignored
rkflashtool: read chip version

Get the chip version from the bootrom.
cf. K_FW_GET_CHIP_VER and FW_GetChipVer() in U-Boot (rockusb)

    $ rkflashtool v

- Marsboard (RK3066)

    rkflashtool: info: rkflashtool v5.2
    rkflashtool: info: Detected RK3066...
    rkflashtool: info: interface claimed
    rkflashtool: info: chip version: 300A-2011.11.11-V101

- Radxa Rock (RK3188)

    rkflashtool: info: rkflashtool v5.2
    rkflashtool: info: Detected RK3188...
    rkflashtool: info: interface claimed
    rkflashtool: info: chip version: 310B-2012.11.30-V100

- Radxa Rock Pro (RK3188)

    rkflashtool: info: rkflashtool v5.2
    rkflashtool: info: Detected RK3188...
    rkflashtool: info: interface claimed
    rkflashtool: info: chip version: 310B-2013.01.31-V101