platform/x86: msi-ec: Fix the build

The msi-ec driver fails to build for me (gcc 7.5):

  CC [M]  drivers/platform/x86/msi-ec.o
drivers/platform/x86/msi-ec.c:72:6: error: initializer element is not constant
    { SM_ECO_NAME,     0xc2 },
      ^~~~~~~~~~~
drivers/platform/x86/msi-ec.c:72:6: note: (near initialization for ‘CONF0.shift_mode.modes[0].name’)
drivers/platform/x86/msi-ec.c:73:6: error: initializer element is not constant
    { SM_COMFORT_NAME, 0xc1 },
      ^~~~~~~~~~~~~~~
drivers/platform/x86/msi-ec.c:73:6: note: (near initialization for ‘CONF0.shift_mode.modes[1].name’)
drivers/platform/x86/msi-ec.c:74:6: error: initializer element is not constant
    { SM_SPORT_NAME,   0xc0 },
      ^~~~~~~~~~~~~
drivers/platform/x86/msi-ec.c:74:6: note: (near initialization for ‘CONF0.shift_mode.modes[2].name’)
(...)

Don't try to be smart, just use defines for the constant strings. The
compiler will recognize it's the same string and will store it only
once in the data section anyway.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Fixes: 392cacf2

 ("platform/x86: Add new msi-ec driver")
Cc: stable@vger.kernel.org
Cc: Nikita Kravets <teackot@gmail.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Mark Gross <markgross@kernel.org>
Link: https://lore.kernel.org/r/20230805101010.54d49e91@endymion.delvare
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>