powerpc: Use lower case for the core names

Freescale documentation presents the PowerPC core names in lower case, such as
"e300", "e500", "e600", etc.

Change the upper case occurrences into lower case so that the core names
reported in U-boot can match the ones from the documentation.

While at it also fix a checkpatch error:

ERROR: space prohibited before that close parenthesis ')'
#53: FILE: arch/powerpc/cpu/mpc86xx/cpu.c:81:
+	printf("e600 Core %d", (msscr0 & 0x20) ? 1 : 0 );

Reported-by: Heinz Wrobel <heinz.wrobel@freescale.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>