elf: Fix comments to EF_MIPS_MACH_xxx constants

elf: Fix comments to EF_MIPS_MACH_xxx constants

Regarding R5900 CPU, some sources indicate that the Emotion Engine
ISA/ASE was designed by Toshiba and licensed to Sony. Others sources
claim it was a joint effort. It therefore makes sense to refer to
the CPU as "Toshiba/Sony R5900".

Also, remove and "'s" in the line for some other CPU, for the sake
of consistency.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reported-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Fredrik Noring <noring@nocrew.org>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>