Geert Uytterhoeven reported that commit 4e244c10 ("kconfig: remove
unneeded symbol_empty variable") changed the default value of
CONFIG_LOG_CPU_MAX_BUF_SHIFT from 12 to 0.

As it turned out, this is an undefined behavior because sym_calc_value()
stopped setting the sym->curr.tri field for 'int', 'hex', and 'string'
symbols.

This commit restores the original behavior, where 'int', 'hex', 'string'
symbols are interpreted as false if used in boolean contexts.

CONFIG_LOG_CPU_MAX_BUF_SHIFT will default to 12 again, irrespective
of CONFIG_BASE_SMALL. Presumably, this is not the intended behavior,
as already reported [1], but this is another issue that should be
addressed by a separate patch.

[1]: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/

Fixes: 4e244c10 ("kconfig: remove unneeded symbol_empty variable")
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>