Remove linker lists (LGAs) from SPL linker scripts

Many SPL linker scripts needlessly include linker lists (aka LGAs).
Remove them whenever possible; keep it only in the seven am335x_evm
variants (am335x_evm, am335x_evm_uart[1-5], am335x_evm_spiboot),
where there is actual content in output section .u_boot_list.

This commit keeps all u-boot.bin and u-boot-spl.bin in ARM targets
byte-identical.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>