xilinx_hwicap: fifo_icap.c: fix all kernel-doc warnings

Modify comments in fifo_icap.c to prevent all kernel-doc warnings:

Warning: fifo_icap.c:51 This comment starts with '/**', but isn't a
kernel-doc comment.
* HwIcap Device Interrupt Status/Enable Registers
Warning: fifo_icap.c:106 No description found for return value
of 'fifo_icap_fifo_read'
Warning: fifo_icap.c:160 No description found for return value
of 'fifo_icap_get_status'
Warning: fifo_icap.c:171 No description found for return value
of 'fifo_icap_busy'
Warning: fifo_icap.c:184 No description found for return value
of 'fifo_icap_write_fifo_vacancy'
Warning: fifo_icap.c:196 No description found for return value
of 'fifo_icap_read_fifo_occupancy'
Warning: fifo_icap.c:207 bad line:
Warning: fifo_icap.c:214 No description found for return value
of 'fifo_icap_set_configuration'
Warning: fifo_icap.c:290 function parameter 'frame_buffer' not described
in 'fifo_icap_get_configuration'
Warning: fifo_icap.c:290 function parameter 'num_words' not described
in 'fifo_icap_get_configuration'
Warning: fifo_icap.c:290 No description found for return value
of 'fifo_icap_get_configuration'
Warning: fifo_icap.c:357 expecting prototype for buffer_icap_reset().
Prototype was for fifo_icap_reset() instead

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Michal Simek <michal.simek@amd.com>
Link: https://patch.msgid.link/20251214191750.2173225-1-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>