m5253demo: Fix static variable in non-static inline function warning

The function 'spin_wheel' is declared as inline, but not static and thus
we see warnings that 'w' and 'p' are declared static in a non-static
inline function.  Correct this by marking spin_wheel as static inline.

Cc: TsiChung Liew <Tsi-Chung.Liew@freescale.com>
Signed-off-by: Tom Rini <trini@konsulko.com>