gpu: arm: midgard: remove choice in Kconfig of r12p0_04rel0

gpu: arm: midgard: remove choice in Kconfig of r12p0_04rel0

The choice of each mali version causes Kconfig errors like below,

$ make ARCH=arm64 menuconfig
scripts/kconfig/mconf  Kconfig
drivers/gpu/arm/midgard/r12p0_04rel0/Kconfig:126:warning: choice value used outside its choice group
drivers/gpu/arm/midgard/r12p0_04rel0/Kconfig:129:warning: choice value used outside its choice group
drivers/gpu/arm/midgard/r12p0_04rel0/Kconfig:132:warning: choice value used outside its choice group
drivers/gpu/arm/midgard/r12p0_04rel0/Kconfig:135:warning: choice value used outside its choice group
drivers/gpu/arm/midgard/r12p0_04rel0/Kconfig:137:warning: choice value used outside its choice group

Also remove configs for unused platform.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>