mtd: r852: Staticize local symbols

mtd: r852: Staticize local symbols

These local symbols are used only in this file.
Fix the following sparse warnings:

drivers/mtd/nand/r852.c:232:6: warning: symbol 'r852_write_buf' was not declared. Should it be static?
drivers/mtd/nand/r852.c:264:6: warning: symbol 'r852_read_buf' was not declared. Should it be static?
drivers/mtd/nand/r852.c:315:6: warning: symbol 'r852_cmdctl' was not declared. Should it be static?
drivers/mtd/nand/r852.c:360:5: warning: symbol 'r852_wait' was not declared. Should it be static?
drivers/mtd/nand/r852.c:389:5: warning: symbol 'r852_ready' was not declared. Should it be static?
drivers/mtd/nand/r852.c:400:6: warning: symbol 'r852_ecc_hwctl' was not declared. Should it be static?
drivers/mtd/nand/r852.c:432:5: warning: symbol 'r852_ecc_calculate' was not declared. Should it be static?
drivers/mtd/nand/r852.c:464:5: warning: symbol 'r852_ecc_correct' was not declared. Should it be static?
drivers/mtd/nand/r852.c:532:6: warning: symbol 'r852_engine_enable' was not declared. Should it be static?
drivers/mtd/nand/r852.c:550:6: warning: symbol 'r852_engine_disable' was not declared. Should it be static?
drivers/mtd/nand/r852.c:560:6: warning: symbol 'r852_card_update_present' was not declared. Should it be static?
drivers/mtd/nand/r852.c:575:6: warning: symbol 'r852_update_card_detect' was not declared. Should it be static?
drivers/mtd/nand/r852.c:589:9: warning: symbol 'r852_media_type_show' was not declared. Should it be static?
drivers/mtd/nand/r852.c:600:1: warning: symbol 'dev_attr_media_type' was not declared. Should it be static?
drivers/mtd/nand/r852.c:604:6: warning: symbol 'r852_update_media_status' was not declared. Should it be static?
drivers/mtd/nand/r852.c:633:5: warning: symbol 'r852_register_nand_device' was not declared. Should it be static?
drivers/mtd/nand/r852.c:671:6: warning: symbol 'r852_unregister_nand_device' was not declared. Should it be static?
drivers/mtd/nand/r852.c:685:6: warning: symbol 'r852_card_detect_work' was not declared. Should it be static?
drivers/mtd/nand/r852.c:824:6: warning: symbol 'r852_probe' was not declared. Should it be static?
drivers/mtd/nand/r852.c:964:6: warning: symbol 'r852_remove' was not declared. Should it be static?
drivers/mtd/nand/r852.c:995:6: warning: symbol 'r852_shutdown' was not declared. Should it be static?

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>