x86/olpc: Fix inconsistent MFD_CS5535 configuration

This Kconfig warning appeared after a fix to the Kconfig validation.
The GPIO_CS5535 driver depends on the MFD_CS5535 driver, but the former
is selected in places where the latter is not:

WARNING: unmet direct dependencies detected for GPIO_CS5535
  Depends on [m]: GPIOLIB [=y] && (X86 [=y] || MIPS || COMPILE_TEST [=y]) && MFD_CS5535 [=m]
  Selected by [y]:
  - OLPC_XO1_SCI [=y] && X86_32 [=y] && OLPC [=y] && OLPC_XO1_PM [=y] && INPUT [=y]=y

The warning does seem appropriate, since the GPIO_CS5535 driver won't
work unless MFD_CS5535 is also present. However, there is no link time
dependency between the two, so this caused no problems during randconfig
testing before.

This changes the 'select GPIO_CS5535' to 'depends on GPIO_CS5535' to
avoid the issue, at the expense of making it harder to configure the
driver (one now has to select the dependencies first).

The 'select MFD_CORE' part is completely redundant, since we already
depend on MFD_CS5535 here, so I'm removing that as well.

Ideally, the private symbols exported by that cs5535 gpio driver would
just be converted to gpiolib interfaces so we could expletely avoid
this dependency.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kbuild@vger.kernel.org
Fixes: f622f827 ("kconfig: warn unmet direct dependency of tristate symbols selected by y")
Link: http://lkml.kernel.org/r/20180404124539.3817101-1-arnd@arndb.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>