erofs: Do not select tristate symbols from bool symbols

The EROFS filesystem has many configurable options, controlled through
boolean Kconfig symbols.  When enabled, these options may need to enable
additional library functionality elsewhere.  Currently this is done by
selecting the symbol for the additional functionality.  However, if
EROFS_FS itself is modular, and the target symbol is a tristate symbol,
the additional functionality is always forced built-in.

Selecting tristate symbols from a tristate symbol does keep modular
transitivity.  Hence fix this by moving selects of tristate symbols to
the main EROFS_FS symbol.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/da1b899e511145dd43fd2d398f64b2e03c6a39e7.1753879351.git.geert+renesas@glider.be


Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>