sh: Drop unreferenced CONFIG_* defines

sh: Drop unreferenced CONFIG_* defines

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

CONFIG_AP325RXA
CONFIG_AP_SH4A_4A
CONFIG_CPU_SH_TYPE_R
CONFIG_ECOVEC
CONFIG_ESPT
CONFIG_MIGO_R
CONFIG_MPR2
CONFIG_MS7720SE
CONFIG_MS7722SE
CONFIG_MS7750SE
CONFIG_R0P7734
CONFIG_R2DPLUS
CONFIG_RSK7203
CONFIG_RSK7264
CONFIG_RSK7269
CONFIG_SH7752EVB
CONFIG_SH7753EVB
CONFIG_SH7757LCR
CONFIG_SH7763RDP
CONFIG_SH7785LCR

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>