ixgbe: Remove pr_cont uses

As pr_cont output can be interleaved by other processes,
using pr_cont should be avoided where possible.

Miscellanea:

- Use a temporary pointer to hold the next descriptions and
  consolidate the pr_cont uses
- Use the temporary buffer to hold the 8 u32 register values and
  emit those in a single go
- Coalesce formats and logging neatening around those changes
- Fix a defective output for the rx ring entry description when
  also emitting rx_buffer_info data

This reduces overall object size a tiny bit too.

$ size drivers/net/ethernet/intel/ixgbe/*.o*
   text	   data	    bss	    dec	    hex	filename
  62167	    728	     12	  62907	   f5bb	drivers/net/ethernet/intel/ixgbe/ixgbe_main.o.new
  62273	    728	     12	  63013	   f625	drivers/net/ethernet/intel/ixgbe/ixgbe_main.o.old

Signed-off-by: Joe Perches <joe@perches.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>