apply-patches.sh: rename targetdir to builddir

targetdir is not the output/target directory as it can suggest.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Tested-by: Ludovic Desroches <ludovic.desroches@atmel.com>
with an armadeus_apf9328_defconfig build
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>