Fix the build error for dualroot chain of trust.

Fix the build error for dualroot chain of trust.

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