ARM: Drop unreferenced CONFIG_* defines named after boards

The following config symbols are only defined once and never referenced
anywhere else:

CONFIG_AT91SAM9263EK
CONFIG_AT91SAM9RLEK
CONFIG_BARIX_IPAM390
CONFIG_BOARD_H2200
CONFIG_EP9301
CONFIG_KZM_A9_GT
CONFIG_PICOSAM
CONFIG_PLATINUM_PICON
CONFIG_PLATINUM_TITANIUM
CONFIG_PM9261
CONFIG_PM9263
CONFIG_PM9G45
CONFIG_SIEMENS_DRACO
CONFIG_SIEMENS_PXM2
CONFIG_SIEMENS_RUT
CONFIG_SMDKC100
CONFIG_SMDKV310
CONFIG_STM32F4DISCOVERY

Most of them are config symbols named after the respective boards which
seems to have been a standard practice at some point.

Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>