Cleanup: fix "MHz" spelling

board/Marvell/db64360/pci.c

board/Marvell/db64460/pci.c

board/amcc/katmai/cmd_katmai.c

board/amcc/yucca/cmd_yucca.c

board/bf537-stamp/post-memory.c

board/cray/L1/L1.c

board/eltec/bab7xx/misc.c

board/esd/cpci750/pci.c

board/esd/pci405/pci405.c

board/fads/fads.c

board/freescale/mpc8540ads/mpc8540ads.c

board/freescale/mpc8541cds/mpc8541cds.c

board/freescale/mpc8555cds/mpc8555cds.c

board/freescale/mpc8560ads/mpc8560ads.c

board/gen860t/beeper.c

board/idmr/idmr.c

board/motionpro/motionpro.c

board/mpc8540eval/mpc8540eval.c

board/mpl/pip405/pip405.c

board/pm854/pm854.c