kconfig: Clean up header comments and make them consistent

Use this short header style in all Kconfig files:

    # <description>

    # <copyright>
    # <license>

    ...

Also change all <description>s from

    # Kconfig[.extension] - Foo-related options

to just

    # Foo-related options

It's clear enough that it's about Kconfig.

The <description> cleanup was done with this command, along with some
manual cleanup (big letter at the start, etc.)

    git ls-files '*Kconfig*' | \
        xargs sed -i -E '1 s/#\s*Kconfig[\w.-]*\s*-\s*/# /'

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>

soc/riscv/openisa_rv32m1/Kconfig

@@ -1,5 +1,4 @@
 # Copyright (c) 2018 Foundries.io Ltd
-#
 # SPDX-License-Identifier: Apache-2.0
 
 # The OpenISA RV32M1 SoC directory in riscv supports the RISC-V

soc/riscv/openisa_rv32m1/Kconfig.defconfig

@@ -1,7 +1,6 @@
-# Kconfig.defconfig: RV32M1 SoC RISC-V core default configuration values
-#
+# RV32M1 SoC RISC-V core default configuration values
+
 # Copyright (c) 2018 Foundries.io Ltd
-#
 # SPDX-License-Identifier: Apache-2.0
 
 if SOC_OPENISA_RV32M1_RISCV32

soc/riscv/openisa_rv32m1/Kconfig.soc

@@ -1,5 +1,4 @@
 # Copyright (c) 2018 Foundries.io Ltd
-#
 # SPDX-License-Identifier: Apache-2.0
 
 config SOC_OPENISA_RV32M1_RISCV32