ARM: OMAP2+: gpmc: make gpmc_cs_get_name() static

Fix sparse warning:
  warning: symbol 'gpmc_cs_get_name' was not declared. Should it be static?

Signed-off-by: Semen Protsenko <semen.protsenko@globallogic.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>