u-boot: Add peach pit chromebook configs

This adds U-Boot configuration for the Samsung Chromebook 2 11", also
known as "peach-pit" in the U-Boot upstream defconfigs. Also adds a
shared "peach" board directory to share with others having the same
baseboard. The config is almost the same as upstream defconfig, but with
REMAKE_ELF and POSITION_INDEPENDENT enabled.

Untested since I don't have the peach pit chromebook.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

resources/u-boot/peach/board.cfg

+ubtree="peach"
+ubrevision="e092e3250270a1016c877da7bdd9384f14b1321e" # v2022.07
+arch="ARMv7"

resources/u-boot/peach_pit/board.cfg

+ubtree="peach"
+arch="ARMv7"