timtest: Fix pstack malloc for task 2 should use TASK2_STACK_SIZE
timtest: Fix pstack malloc for task 2 should use TASK2_STACK_SIZE

wes3/incubator-mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core,andrzej-kaczmarek/apache-mynewt-core,IMGJulian/incubator-mynewt-core,mlaz/mynewt-core,IMGJulian/incubator-mynewt-core,wes3/incubator-mynewt-core,IMGJulian/incubator-mynewt-core,andrzej-kaczmarek/incubator-mynewt-core,IMGJulian/incubator-mynewt-core,andrzej-kaczmarek/incubator-mynewt-core,IMGJulian/incubator-mynewt-core,andrzej-kaczmarek/apache-mynewt-core,wes3/incubator-mynewt-core,andrzej-kaczmarek/incubator-mynewt-core,andrzej-kaczmarek/incubator-mynewt-core,andrzej-kaczmarek/apache-mynewt-core,andrzej-kaczmarek/apache-mynewt-core,wes3/incubator-mynewt-core,mlaz/mynewt-core,andrzej-kaczmarek/incubator-mynewt-core,mlaz/mynewt-core,wes3/incubator-mynewt-core