boards: *: remove SPI_*_EN now rework is merged

boards/arduino-common/include/periph_conf.h

boards/arduino-mega2560/include/periph_conf.h

boards/avsextrem/include/periph_conf.h

boards/msb-430/include/periph_conf.h

boards/msb-430h/include/periph_conf.h

boards/telosb/include/periph_conf.h

boards/waspmote-pro/include/periph_conf.h

boards/wsn430-common/include/periph_conf.h

boards/z1/include/periph_conf.h

cpu/atmega_common/periph/spi.c