platform/x86: thinkpad_acpi: Fix old style declaration GCC warning

Fix an [-Wold-style-declaration] GCC warning by moving the inline
keyword before the return type.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>