This patch redefines the variable LIBC_SRCS for Tegra platforms,
to remove unused libc files from the list. This patch is a building
block to eventually use other libc implementations in the future.

Change-Id: Iccde5a75f5e2d6f4e2dbc6274beb423b80e846fd
Signed-off-by: Anthony Zhou <anzhou@nvidia.com>
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>