boards/msp430-based: removed flashpage feature

This feature is already defined by the (common) CPU implementation,
so no need to re-define it for each board.

boards/msb-430/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
-FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_gpio
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

boards/msb-430h/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
 FEATURES_PROVIDED += periph_gpio
-FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer
 FEATURES_PROVIDED += periph_uart

boards/telosb/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
-FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_gpio
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

boards/wsn430-v1_3b/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
-FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_gpio
 FEATURES_PROVIDED += periph_timer
 FEATURES_PROVIDED += periph_spi

boards/wsn430-v1_4/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
-FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_gpio
 FEATURES_PROVIDED += periph_timer
 FEATURES_PROVIDED += periph_spi

boards/z1/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
-FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_gpio
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer