bcma: keep *config menu together

Use "if BCMA"/"endif" around all Kconfig symbols so that they are
kept together in *config menus instead of showing up in unexpected
places. Also remove "depends on BCMA" since this is handled by the
"if BCMA" addition.

Tested with ARCH={x86_64,MIPS} using make {n,menu,g,x}config.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>