binman: openssl: x509: ti_secure_rom: Add support for bootcore_opts

According to the TRMs of K3 platform of devices, the ROM boot image
format specifies a "Core Options Field" that provides the capability to
set the boot core in lockstep when set to 0 or to split mode when set
to 2. Add support for providing the same from the binman DTS. Also
modify existing test case for ensuring future coverage.

Signed-off-by: Neha Malcom Francis <n-francis@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>