Fixed build error for dualroot chain of trust.
Build error were thrown as below while compiling the code for
dualroot chain of trust:

aarch64-none-elf-ld.bfd: ./build/fvp/debug/bl1/tbbr_cot_bl1.o:
(.bss.auth_img_flags+0x0): multiple definition of `auth_img_flags';
./build/fvp/debug/bl1/cot.o:(.bss.auth_img_flags+0x0): first defined here

aarch64-none-elf-ld.bfd: ./build/fvp/debug/bl1/tbbr_cot_bl1.o:
(.rodata.cot_desc_size+0x0): multiple definition of `cot_desc_size';
./build/fvp/debug/bl1/cot.o:(.rodata.cot_desc_size+0x0): first defined here

aarch64-none-elf-ld.bfd: ./build/fvp/debug/bl1/tbbr_cot_bl1.o:
(.rodata.cot_desc_ptr+0x0): multiple definition of `cot_desc_ptr';
./build/fvp/debug/bl1/cot.o:(.rodata.cot_desc_ptr+0x0): first defined here


Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: I1a426c4e7f5f8013d71dafc176c7467c1b329757