platform/x86: thinkpad_acpi: Fix 'warning: no previous prototype for' warnings

platform/x86: thinkpad_acpi: Fix 'warning: no previous prototype for' warnings

Some of the new dytc handling functions are not marked static, even though
they are only used internally.

Mark these static, fixing the following compiler warnings:

drivers/platform/x86/thinkpad_acpi.c:10081:5: warning: no previous prototype for 'dytc_profile_get' [-Wmissing-prototypes]
drivers/platform/x86/thinkpad_acpi.c:10095:5: warning: no previous prototype for 'dytc_cql_command' [-Wmissing-prototypes]
drivers/platform/x86/thinkpad_acpi.c:10133:5: warning: no previous prototype for 'dytc_profile_set' [-Wmissing-prototypes]

Cc: Mark Pearson <markpearson@lenovo.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210204140158.268289-1-hdegoede@redhat.com