pogo_v4: Disable LTO

With gcc-12.2 we now get:
lib/zlib/inflate.c:360: undefined reference to `__gnu_thumb1_case_si'
when building this platform. This seems like some odd problem with LTO
and Thumb, but since the platform continues to link, I assume it's
within size constraints, so lets just disable LTO for now.

Cc: Tony Dinh <mibodhi@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>