docs: Allwinner clarifications about availability
docs: Allwinner clarifications about availability

The A80 boards exist in both locked (publicly available) an unlocked
versions (to Allwinner partners). Our main documentation has been
updated clarifying that this is the case.

Signed-off-by: Joakim Bech <741f90e2a7f4d9afbad8bd50be20560f4cf38962@linaro.org>
Reviewed-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>
Reviewed-by: Sunny <b892f067921d231448e8f0a591107de8b2ad3202@allwinnertech.com>

matt2048/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os,matt2048/optee_os,cedric-chaumont-st-dev/optee_os,cedric-chaumont-st-dev/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os,cedric-chaumont-st-dev/optee_os,matt2048/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,Microsoft/optee_os,Microsoft/optee_os,cedric-chaumont-st-dev/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os