ARM: ep93xx: Make ts72xx_register_flash() static

ARM: ep93xx: Make ts72xx_register_flash() static

... and fix the warning/error:

arch/arm/mach-ep93xx/ts72xx.c:154:13: error: no previous prototype for function 'ts72xx_register_flash' [-Werror,-Wmissing-prototypes]
void __init ts72xx_register_flash(struct mtd_partition *parts, int n,
            ^
arch/arm/mach-ep93xx/ts72xx.c:154:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
void __init ts72xx_register_flash(struct mtd_partition *parts, int n,
^
static

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Link: https://lore.kernel.org/lkml/202202140141.HRZ3WZwi-lkp@intel.com/T/
Link: https://lore.kernel.org/r/20220523065616.325052-1-alexander.sverdlin@gmail.com'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>