ipmi: ASPEED_BT_IPMI_BMC: select REGMAP_MMIO instead of depending on it

ipmi: ASPEED_BT_IPMI_BMC: select REGMAP_MMIO instead of depending on it

REGMAP is a hidden (not user visible) symbol. Users cannot set it
directly thru "make *config", so drivers should select it instead of
depending on it if they need it.

Consistently using "select" or "depends on" can also help reduce
Kconfig circular dependency issues.

Therefore, change the use of "depends on REGMAP_MMIO" to
"select REGMAP_MMIO", which will also set REGMAP.

Fixes: eb994594bc22 ("ipmi: bt-bmc: Use a regmap for register access")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrew Jeffery <andrew@aj.id.au>
Cc: Corey Minyard <minyard@acm.org>
Cc: openipmi-developer@lists.sourceforge.net
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Message-Id: <20230226053953.4681-2-rdunlap@infradead.org>
Signed-off-by: Corey Minyard <cminyard@mvista.com>