Rename text region in ARM linker file for a few NXP CPUs

[davidsaada]

Description

In most of the linker files for the ARM toolchain, the text region has a uniform name LR_IROM1. However, a few Freescale/NXP boards had the LR_m_text name instead. Beside this being not uniform, it doesn't allow us to determine the text region size at run time (which is required in a few future tests). In addition, the LR_IROM1 name is referred to in a few Handbook documents (like Bootstrap or Flash) and the LR_m_text name deviates from this documentation.
This change currently has no effect on anything other than the linker files themselves (These names aren't mentioned in the code).

Pull request type

[x] Fix
[ ] Refactor
[ ] New target
[ ] Feature
[ ] Breaking change

[0xc0170]

which is required in a few future tests

@davidsaada Thanks for fixing it. If this is going to be unified, we should document it and have this tested.

[0xc0170]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2382
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7242/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : FAILURE

Build number : 2015
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7242/

[0xc0170]

/morph export-build

[davidsaada]

Thanks for fixing it. If this is going to be unified, we should document it and have this tested.

Right. Will have separate PRs for it. Need to think of the test - It's not really a test, as the acceptance here is a successful build.

[mbed-ci]

Test : SUCCESS

Build number : 2171
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7242/2171

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2018
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7242/