uniphier: make uniphier_mmap_setup() work with PIE

uniphier: make uniphier_mmap_setup() work with PIE

BL2_BASE, BL31_BASE, and BL32_BASE are defined in platform_def.h,
that is, determined at link-time.

On the other hand, BL2_END, BL31_END, and BL32_END are derived from
the symbols produced by the linker scripts. So, they are fixed-up
at run-time if ENABLE_PIE is enabled.

To make it work in a position-indepenent manner, use BL_CODE_BASE and
BL_END, both of which are relocatable.

Change-Id: Ic179a7c60eb64c5f3024b178690b3ac7cbd7521b
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>