ARM: fix u-boot.lds for -ffunction-sections/-fdata-sections

When -ffunction-sections or -fdata-section are used, symbols are placed
into sections such as .data.eserial1_device and .bss.serial_current.
Update the linker script to explicitly include these. Without this
change (at least with my gcc-4.5.3 built using crosstool-ng), I see that
the sections do end up being included, but __bss_end__ gets set to the
same value as __bss_start.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Allen Martin <amartin@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>