ARM: hawkboard: fix compilation of nand_spl

ARM: hawkboard: fix compilation of nand_spl

Fix build problem:

nand_spl/board/davinci/da8xxevm/hawkboard_nand_spl.c: In function 'board_init_f':
nand_spl/board/davinci/da8xxevm/hawkboard_nand_spl.c:132: warning: implicit declaration of function 'nand_boot'
nand_spl/board/davinci/da8xxevm/hawkboard_nand_spl.c:133: warning: 'noreturn' function does return

Signed-off-by: Wolfgang Denk <[email protected]>
Cc: Syed Mohammed Khasim <[email protected]>
Cc: Sughosh Ganu <[email protected]>
Cc: Albert ARIBAUD <[email protected]>