feat(plat/arm): Introduce TC1 platform

This renames tc0 platform folder and files to tc, and introduces
TARGET_PLATFORM variable to account for the differences between
TC0 and TC1.

Signed-off-by: Usama Arif <usama.arif@arm.com>
Change-Id: I5b4a83f3453afd12542267091b3edab4c139c5cd
diff --git a/docs/plat/arm/index.rst b/docs/plat/arm/index.rst
index f50dab5..c834f6a 100644
--- a/docs/plat/arm/index.rst
+++ b/docs/plat/arm/index.rst
@@ -8,7 +8,7 @@
    juno/index
    fvp/index
    fvp-ve/index
-   tc0/index
+   tc/index
    arm_fpga/index
    arm-build-options
    morello/index