siemens: Quote A/B flags in env tests

The Siemens am33x-common, env-common and draco-etamin headers gate
boot-partition selection logic on:

    if test -n ${A}; then ...
    if test -n ${B}; then ...

A and B are flags that the upgrade machinery sets to mark "the other
partition just became active".  The default state is unset, in which
case the expression expands to 'test -n' with no operand and relies
on a U-Boot 'test' quirk that treats a missing operand as false to
skip the branch.

Quote each variable so an unset A or B expands to 'test -n ""' and
the emptiness check is explicit.

Fixes: 8b0619579b22 ("cmd: test: fix handling of single-argument form of test")
Signed-off-by: Simon Glass <[email protected]>

0 files changed, 0 insertions, 0 deletions