powerpc/mpc52xx_lpbfifo: fix all kernel-doc warnings

Fix multiple kernel-doc warnings in mpc52xx_lpbfifo.c:

arch/powerpc/platforms/52xx/mpc52xx_lpbfifo.c:377: warning: expecting prototype for mpc52xx_lpbfifo_bcom_poll(). Prototype was for mpc52xx_lpbfifo_poll() instead

mpc52xx_lpbfifo.c:221: warning: No description found for return value of 'mpc52xx_lpbfifo_irq'
mpc52xx_lpbfifo.c:327: warning: No description found for return value of 'mpc52xx_lpbfifo_bcom_irq'
mpc52xx_lpbfifo.c:398: warning: No description found for return value of 'mpc52xx_lpbfifo_submit'

mpc52xx_lpbfifo.c:64: warning: Function parameter or member 'req' not described in 'mpc52xx_lpbfifo_kick'
mpc52xx_lpbfifo.c:220: warning: contents before sections
mpc52xx_lpbfifo.c:223: warning: Function parameter or member 'irq' not described in 'mpc52xx_lpbfifo_irq'
mpc52xx_lpbfifo.c:223: warning: Function parameter or member 'dev_id' not described in 'mpc52xx_lpbfifo_irq'
mpc52xx_lpbfifo.c:328: warning: contents before sections
mpc52xx_lpbfifo.c:331: warning: Function parameter or member 'irq' not described in 'mpc52xx_lpbfifo_bcom_irq'
mpc52xx_lpbfifo.c:331: warning: Function parameter or member 'dev_id' not described in 'mpc52xx_lpbfifo_bcom_irq'

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221124061918.1967-1-rdunlap@infradead.org