treewide: remove _defconfig="defconfig" as it is default

_defconfig="defconfig" is the default logic in pmbootstrap, and thus should not be
duplicated in kernel packages. The only use-case for _defconfig is for when the
defconfig differs from what is automatically selected.

linux-next is not modified because it still uses the old kconfig fragments logic and
would break with this change.

Signed-off-by: Aster Boese <asterboese@mailbox.org>
Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/8978>

device/community/linux-postmarketos-qcom-sdm845/APKBUILD

@@ -29,7 +29,6 @@ makedepends="
 "
 
 _tag="sdm845-7.1-rc1-r0"
-_defconfig="defconfig"
 
 # Source
 source="

device/main/linux-postmarketos-lts/APKBUILD

@@ -77,7 +77,6 @@ source="
 	config-lts.x86_64
 "
 builddir="$srcdir/linux-$_kver"
-_defconfig="defconfig"
 
 if [ "${pkgver%.0}" = "$pkgver" ]; then
 	# Prepend to apply first

device/main/linux-postmarketos-mainline/APKBUILD

@@ -72,7 +72,6 @@ source="
 	config-mainline.x86_64
 "
 builddir="$srcdir/linux-${pkgver/_/-}"
-_defconfig="defconfig"
 
 case "$CARCH" in
 	aarch64*) _carch="arm64" ;;

device/main/linux-postmarketos-stable/APKBUILD

@@ -74,7 +74,6 @@ source="
 	config-stable.x86_64
 "
 builddir="$srcdir/linux-$_kver"
-_defconfig="defconfig"
 
 if [ "${pkgver%.0}" = "$pkgver" ]; then
 	# Prepend to apply first

device/testing/linux-ayaneo-pocket-s2/APKBUILD

@@ -44,7 +44,6 @@ makedepends="
 _url="https://gitlab.com/superna9999/"
 _repository="linux"
 _commit="d42f74bb3f3372e95cd0525177e2cb83ebb23b17"
-_defconfig="defconfig"
 _config="config-$_flavor.$arch"
 source="
 	$pkgname-$_commit.tar.gz::$_url/$_repository/-/archive/$_commit/$_repository-$_commit.tar.gz

device/testing/linux-postmarketos-amlogic/APKBUILD

@@ -34,7 +34,6 @@ makedepends="
 	python3
 	zstd
 "
-_defconfig="defconfig"
 _config="
 	config-$_flavor.$arch
 	amlogic.config

device/testing/linux-postmarketos-asahi/APKBUILD

@@ -57,7 +57,6 @@ source="
 	enable-dynamic-ftrace.patch
 "
 builddir="$srcdir/linux-asahi-$_asahiver"
-_defconfig="defconfig"
 
 prepare() {
 	default_prepare