bcm27xx: clean up stray config-6.18/config-6.12 entries

bcm27xx: clean up stray config-6.18/config-6.12 entries

Remove stray/redundant lines from the shared kernel config fragments,
in both config-6.18 and config-6.12:

- CONFIG_COMMON_CLK_RP1_SDIO is listed twice (the second copy has a
  double space before "is not set", which is why dedup tooling never
  caught it).
- CONFIG_WS2812_PIO_RP1, CONFIG_PWM_PIO_RP1, and CONFIG_RP1_PIO are
  each the KCONFIG of a kmod package in modules/other.mk, so
  gen_kconfig_overrides() already emits "# ... is not set" for all
  three whenever their package is unselected, independently of these
  fragments.

No functional change.

Signed-off-by: Joshua Covington <joshuacov@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/24645
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>