src/cpu/amd/model_fxx/powernow_api.c Fix checkpatch errors + warnings

Fix line over 80 characters, spaces required around comparisons,space
required after close brace '}', comma ',', semicolon ';',  space
prohibited after ')' errors and warnings

Change-Id: I5585f55a606d4f2149b17ac92cbdd832f242630e
Signed-off-by: Evelyn Huang <evhuang@google.com>
Reviewed-on: https://review.coreboot.org/20099
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>